The Justice Department appointed a special counsel Wednesday to investigate possible coordination between President Trump’s associates and Russian officials — a clear signal to the White House that federal investigators will aggressively pursue the matter despite the president’s insistence that there was no “collusion’’ with the Kremlin. 
 
 Robert S. Mueller III, a former prosecutor who served as the FBI director from 2001 to 2013, has agreed to take over the investigation as a special counsel, Deputy Attorney General Rod J. Rosenstein announced. The move marks a concession by the Trump administration to Democratic demands for the investigation to be run independently of the Justice Department. Calls for a special counsel intensified after Trump fired FBI Director James B. Comey last week. 
 
 [Everything you need to know about the Russia investigation’s ‘special counsel’] 
 
 “In my capacity as acting attorney general I determined that it is in the public interest for me to exercise my authority and appoint a special counsel to assume responsibility for this matter,’’ Rosenstein said in a statement. “My decision is not a finding that crimes have been committed or that any prosecution is warranted. I have made no such determination. What I have determined is that based upon the unique circumstances the public interest requires me to place this investigation under the authority of a person who exercises a degree of independence from the normal chain of command.” 
 
 Mueller, often described by those who worked for him as a stern and press-averse disciplinarian, issued a characteristically terse statement: “I accept this responsibility and will discharge it to the best of my ability.’’ 
 
 (Victoria Walker,Jayne Orenstein,Dalton Bennett,Jenny Starrs/The Washington Post) 
 
 Trump reacted to the news by saying “a thorough investigation will confirm what we already know — there was no collusion between my campaign and any foreign entity. I look forward to this matter concluding quickly. In the meantime, I will never stop fighting for the people and the issues that matter most to the future of our country.” 
 
 In a series of tweets early Thursday, Trump decried that a special counsel was not named to investigate what he alleged were “illegal acts” by the Obama administration and the campaign of Hillary Clinton. 
 
 “With all of the illegal acts that took place in the Clinton campaign & Obama Administration, there was never a special councel appointed!,” Trump wrote, misspelling the word counsel. 
 
 Less than 15 minutes later, he tweeted: “This is the single greatest witch hunt of a politician in American history!” 
 
 The White House did not learn of Rosenstein’s decision until just 30 minutes before the public announcement was made. Rosenstein called White House Counsel Donald McGahn at 5:30 p.m. to inform him, at which point McGahn walked downstairs from his second-floor office to the Oval Office to notify Trump. 
 
 Trump summoned his senior staff to the Oval Office, and together they drafted a statement reacting to the decision, coming from the president, that was distributed to reporters shortly after 7 p.m. 
 
 One senior White House official who was present for the discussions described Trump as “unbelievably calm and measured.” 
 
 “I expected him to be ranting and raving, but he was like, ‘Fine, let them do what they have to do, but we’ll be focused on our agenda,’ ” said this official, who spoke on the condition of anonymity to describe the private talks. 
 
 Democrats cheered the announcement as a step forward in resolving the unanswered questions about Russian meddling in last year’s presidential election — and whether the president or anyone at the White House has interfered with the investigation. 
 
 [Here’s how an independent investigation into Trump and Russia would happen] 
 
 Sen. Richard Blumenthal (D-Conn.) said Mueller “has the expertise and experience, guts and backbone to uncover the truth.’’ He said Mueller must be given all the resources necessary to “pursue the facts wherever they lead,’’ including whether anyone may have tried to obstruct justice. 
 
 Rep. Jason Chaffetz (R-Utah), chairman of the House Oversight and Government Reform Committee, cheered the choice, writing on Twitter: “Impeccable credentials. Should be widely accepted.” 
 
 But some Democrats said Mueller’s appointment does not preclude the need for an independent commission to examine Russian interference in the election. 
 
 “An independent commission doesn’t govern the FBI investigation, an independent commission doesn’t make charging decisions,” said Rep. Adam B. Schiff (Calif.), the ranking Democrat on the House Intelligence Committee, which is conducting its own probe of Russian meddling. “The value an independent commission adds is you have a body that is truly independent of any political consideration. And also has all the resources it needs and a single focus on the oversight of what Russia did, how we need to respond in the future, and it brings that political independence and staff and resources on task. So those are two different needs, and I think they’re complementary, not in competition with each other.” 
 
 The special counsel law grants Mueller the authority to probe possible attempts to stymie his investigation. 
 
 The decision to appoint a special counsel comes a day after revelations that notes taken by Comey in February recount a conversation with the president in which Trump asked him to drop an investigation into his former national security adviser, Michael Flynn. Associates of Comey said he took detailed notes of multiple conversations with the president, and lawmakers are now demanding access to those memos and any other related records held at the FBI. 
 
 The decision also comes amid intense pressure on the senior official who has been overseeing the Russia probe, Rosenstein, to appoint a special counsel. 
 
 Rosenstein was put in charge of the Russia probe after Attorney General Jeff Sessions recused himself. Democrats have challenged Rosenstein’s impartiality in the Russia probe because he wrote a memorandum initially used as the rationale for Comey’s firing. In the memo, Rosenstein said Comey had violated long-standing Justice Department practices in his handling of the investigation into Clinton’s use of a private email server, but shortly after the announcement of the firing, the president said he had decided to fire Comey before he received the recommendation from Rosenstein. 
 
 Rosenstein is scheduled to brief the full Senate in a closed session on Thursday. 
 
 Former colleagues said Rosenstein’s move may help restore his battered reputation among current and former government lawyers. “He got absolutely pummeled by people that he knows,” said a former senior Obama administration lawyer, who spoke on the condition of anonymity to talk candidly. “I think this move, as so often happens in Washington, where there is the opportunity to wash away your sins, was a thorough scrubbing.” 
 
 Under the order signed Wednesday by Rosenstein, Mueller is tasked with investigating “any links and/or coordination between the Russian government and individuals associated with the campaign of President Donald Trump’’ as well as “any matters that arose or may arise directly from the investigation’’ and any other matters that fall under the scope of the Justice Department regulation covering special counsel appointments. 
 
 It wasn’t immediately clear from the language of the order where Mueller might draw the lines as to which matters are related to the Russia investigation. 
 
 That language seems to suggest that Mueller could also take over ongoing investigations into leaks of classified information connected to the Russia probe. As the FBI director, Mueller assiduously discouraged leaks by his subordinates and oversaw investigations that sought to criminally charge leakers of government secrets. 
 
 “If the special counsel believes it is necessary and appropriate, the special counsel is authorized to prosecute federal crimes arising from the investigation of these matters,’’ the order states. 
 
 Another potential legal complication could arise from the law firm where Mueller worked until his appointment as special counsel. That firm, WilmerHale, has represented Trump’s former campaign chairman Paul Manafort, who has been under investigation relating to his work and payments for advising Ukrainian government officials. Officials referred questions about possible recusals on those subjects to Mueller, who didn’t respond to requests for comment. 
 
 Officials said the appointment was being made under a Justice Department statute that has only been used once, in 1999, although the Justice Department has made other special counsel appointments more recently under different authority. 
 
 Peter Zeidenberg, who has worked for a past special counsel, called Mueller an “inspired choice’’ because he comes to the job with automatic credibility among both parties. 
 
 “He’s nominally a Republican, but he’s really not a political person at all,’’ said Zeidenberg, a lawyer now in private practice, who cautioned that such an investigation is likely to take a long time and may not ultimately satisfy the public’s demand for a full accounting. “People are waiting for public answers to what happened, but that’s not his job. There won’t be a report or a news conference at the end of this from him, that’s not his role.’’ 
 
 When he was FBI director, Mueller worked closely for a time with Comey — who as deputy attorney general was nominally Mueller’s boss during the George W. Bush administration — and while the two men agree on much, they have very different personalities. Mueller was a harsh taskmaster who eschewed expressions of warmth with his staff. Comey, in contrast, has written holiday greetings to staff that have been described as moving. 
 
 The special counsel gets money and personnel from the Justice Department, but Mueller can ask for specific individuals to join the case. WilmerHale lawyers James Quarles and Aaron Zebley also stepped down from WilmerHale Wednesday, and a firm spokesman said they were expected to join Mueller. Zebley, a former FBI agent and assistant U.S. attorney, was Mueller’s chief of staff at the FBI. Quarles was an assistant special prosecutor on the Watergate Special Prosecution Force. 
 
 Given the extremely sensitive nature of the counterintelligence probe, it is likely that Mueller will also work with many of the current FBI agents assigned to the case, although the decision is ultimately his to make. The budget for the investigation will still have to be approved by Rosenstein. 
 
 In his new role, Mueller answers to, and in theory could be fired by, Rosenstein, but in practice a special counsel is not subject to daily supervision by any Justice Department official. And given that Mueller’s appointment came about largely because of the firing of the FBI director, it would probably touch off a new political firestorm if Mueller were ever dismissed. 
 
 Philip Rucker, Ellen Nakashima and Julie Tate contributed to this report. 
 
 Read more: 
 
 House majority leader to colleagues in 2016: ‘I think Putin pays’ Trump 
 
 The worst job in Washington right now: Working for Trump ||||| President Donald Trump said the truth would only come out if lawmakers get access to documents they have been thwarted from obtaining. | Chip Somodevilla/Getty Images Trump responds to new FBI informant reports 
 
 President Donald Trump on Saturday appeared to respond to new reports that an FBI informant had reached out to multiple campaign aides during the 2016 presidential campaign. 
 
 "If the FBI or DOJ was infiltrating a campaign for the benefit of another campaign, that is a really big deal," the president wrote on Twitter. 
 
 Story Continued Below 
 
 On Friday night, The New York Times reported that an unnamed FBI informant talked to two campaign advisers who allegedly had suspicious contacts with individuals linked to Russia. The Times did not name the informant but described the person as an "American academic who teaches in Britain" and who made contact with Trump foreign policy advisers George Papadopoulos and Carter Page. 
 
 The alleged informant's name has been published by conservative media outlets and circulated widely on Twitter. 
 
 Earlier Friday, apparently responding to previous conservative media reports, Trump had tweeted: "Reports are there was indeed at least one FBI representative implanted, for political purposes, into my campaign for president. It took place very early on, and long before the phony Russia Hoax became a 'hot' Fake News story. If true - all time biggest political scandal!" 
 
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 Trump's Saturday response shifted from alleging an FBI source was "implanted" into the campaign to suggesting the campaign was "infiltrated." He maintained any such FBI action was politically motivated. There's no indication that was the case. 
 
 Papadopoulos' April 2016 conversation with an Australian diplomat indicating the Russians had so-called dirt on Democratic nominee Hillary Clinton reportedly started the FBI investigation that has led to special counsel Robert Mueller's probe into whether Trump campaign officials colluded with the Russian government during a Kremlin campaign to meddle in the 2016 election. 
 
 Trump added that the truth about the alleged FBI informant could only come out with "the release or review of documents that the House Intelligence Committee (also, Senate Judiciary) is asking for." 
 
 Congressional Republicans have engaged in an intense fight with the Justice Department over access to highly sensitive and classified information about the investigation into the Trump campaign, and the identity of the FBI's informant, and have routinely expressed frustration with DOJ's refusals to grant access to the documents. 
 
 House Freedom Caucus co-founder Rep. Jim Jordan (R-Ohio) said Friday that if the reports about an informant are true, "that is as wrong as it gets." ||||| FILE - In this Thursday, May 17, 2018, file photo, U.S. President Donald Trump speaks during a meeting in the Cabinet Room of the White House, in Washington. Trump said he will "demand" that the Justice... (Associated Press) 
 
 FILE - In this Thursday, May 17, 2018, file photo, U.S. President Donald Trump speaks during a meeting in the Cabinet Room of the White House, in Washington. Trump said he will "demand" that the Justice Department open an investigation into whether the FBI infiltrated his presidential campaign, an extraordinary... (Associated Press) 
 
 FILE - In this Thursday, May 17, 2018, file photo, U.S. President Donald Trump speaks during a meeting in the Cabinet Room of the White House, in Washington. Trump said he will "demand" that the Justice Department open an investigation into whether the FBI infiltrated his presidential campaign, an extraordinary... (Associated Press) FILE - In this Thursday, May 17, 2018, file photo, U.S. President Donald Trump speaks during a meeting in the Cabinet Room of the White House, in Washington. Trump said he will "demand" that the Justice... (Associated Press) 
 
 WASHINGTON (AP) — President Donald Trump said he will "demand" that the Justice Department investigate whether the FBI infiltrated his presidential campaign, an extraordinary order that came hours before his legal team said the special counsel indicated the investigation into the president could be concluded by September. 
 
 Trump tweeted Sunday: "I hereby demand, and will do so officially tomorrow, that the Department of Justice look into whether or not the FBI/DOJ infiltrated or surveilled the Trump Campaign for Political Purposes - and if any such demands or requests were made by people within the Obama Administration!" 
 
 Trump's demand puts further pressure on the Justice Department, which later Sunday asked its inspector general to expand an existing investigation into the Russia probe by examining whether there was any improper politically motivated surveillance. It comes as the White House tries to combat the threat posed by special counsel Robert Mueller's investigation into potential ties between Russia and the Trump campaign. 
 
 The president's lawyer, Rudy Giuliani, said Mueller recently shared a timetable that suggested his probe could end by Sept. 1 if Trump were to sit for an interview in July, which is the legal team's new working plan. 
 
 "We said to them, 'If we're going to be interviewed in July, how much time until the report gets issued?'" Giuliani told The Associated Press on Sunday, referring to the report Mueller is expected to issue to Congress at the conclusion of his investigation. "They said September, which is good for everyone, because no one wants this to drag into the midterms." 
 
 Giuliani said he did not want a repeat of what happened in 2016, when FBI Director James Comey announced in the campaign's final days that he was reopening the investigation into Hillary Clinton's use of a private email server, a decision Democrats believe cost Clinton the race. Giuliani, the former mayor of New York, also said Mueller's team indicated that the entire probe could end by September, not just its investigation into potential obstruction of justice. 
 
 "This would be the culmination of the investigation into the president," Giuliani said. 
 
 The special counsel's office did not respond to a request for comment. 
 
 It is not certain that Trump will sit for an interview with Mueller, though the president has publicly said he would. Giuliani said a decision would not be made until after Trump's summit with North Korean leader Kim Jong Un in Singapore, which is slated for June 12. Giuliani said Sunday the two sides "were getting closer" to agreeing on the parameters on a potential interview but would not put the odds of it happening at better than 50/50. 
 
 Giuliani's apparent attempt to publicly pressure Mueller on the timeline amid interview negotiations came just hours after Trump's demand for a new inquiry, which moved beyond his usual blustery accusations of institutional wrongdoing and into the realm of applying presidential pressure on the Justice Department, a move few of his predecessors have made. 
 
 Trump made the order amid days of public venting about the special counsel investigation, which he has deemed a "witch hunt" that he says has yielded no evidence of collusion between his campaign and Russia. In response, the Justice Department moved Sunday to defuse a growing confrontation with the White House by asking its watchdog to investigate whether there was inappropriate surveillance. 
 
 It was not immediately clear if that move would satisfy Trump, or if any further demands could lead to a confrontation with FBI Director Christopher Wray or Deputy Attorney General Rod Rosenstein, who is overseeing the Mueller investigation. Rosenstein released a statement Sunday saying, "If anyone did infiltrate or surveil participants in a presidential campaign for inappropriate purposes, we need to know about it and take appropriate action." 
 
 The Justice Department probe had begun in March at the request of Attorney General Jeff Sessions and congressional Republicans. Sessions and the lawmakers had urged Inspector General Michael Horowitz to review whether FBI and Justice Department officials abused their surveillance powers by using information compiled by Christopher Steele, a former British spy, and paid for by Democrats to justify monitoring Carter Page, a former campaign adviser to Trump. 
 
 Horowitz said his office will look at those claims as well as communications between Steele and DOJ and FBI officials. 
 
 Trump did not elaborate on the promised "demand," which he included in one of a series of tweets he sent throughout the day Sunday. On Saturday, Trump tweeted, "If the FBI or DOJ was infiltrating a campaign for the benefit of another campaign, that is a really big deal." He said only the release or review of documents the House Intelligence Committee is seeking from the Justice Department "can give conclusive answers." 
 
 Rep. Adam Schiff of California, the senior Democrat on the House Intelligence Committee, called Trump's claim of an embedded spy "nonsense." 
 
 "His 'demand' DOJ investigate something they know to be untrue is an abuse of power, and an effort to distract from his growing legal problems," Schiff tweeted. "Never mind that DOJ has warned that lives and alliances are at risk. He doesn't care." 
 
 Trump's extraordinary demand of the Justice Department alarmed many observers, who felt it not only violated presidential protocol but also could have a chilling effect on federal law enforcement or its use of informants. Giuliani defended the president's actions. 
 
 "As the president's lawyer, I can't be concerned on what effect it may have," he said. "To me, there's not much of a difference between an informant's ongoing collection of information in a surreptitious way or a spy. 
 
 "If this guy was an FBI implant into the campaign," Giuliani said, "that's as offensive as Watergate." 
 
 The New York Times was the first to report that the FBI had an informant who met several times with Trump campaign officials who had suspicious contacts linked to Russia. 
 
 Giuliani said the information discovered by the source should eventually be made public and released to Congress, even if the source's identity is kept confidential. 
 
 The GOP-led House Intelligence Committee closed its Russian meddling probe last month, saying it found no evidence of collusion or coordination between Trump's campaign and Russia. Schiff and other committee Democrats were furious and argued that Republicans had not subpoenaed many witnessed they considered essential to the committee's work. 
 
 Sunday was not the first time that Trump accused his predecessor of politically motivated activity against him. 
 
 Without substantiation, Trump tweeted in March 2017 that former President Barack Obama had conducted surveillance the previous October at Trump Tower, the New York skyscraper where Trump ran his campaign and transition and maintains a residence. Comey later testified to Congress that internal reviews found no information to support the president's tweets. Trump fired Comey over the bureau's Russia investigation. 
 
 ___ 
 
 Lemire reported from New York. Associated Press writer Eric Tucker contributed to this report. 
 
 ___ 
 
 Follow Lemire on Twitter at http://twitter/com/@JonLemire and Superville at http://www.twitter.com/dsupervilleap
– President Trump took another leap into uncharted territory Sunday with a demand for the Justice Department to investigate whether the FBI infiltrated his 2016 campaign. Trump tweeted that he would officially demand Monday that the department "look into whether or not the FBI/DOJ infiltrated or surveilled the Trump Campaign for Political Purposes - and if any such demands or requests were made by people within the Obama Administration!" In what the Washington Post describes as an effort to avoid a bigger showdown, the Justice Department bowed to the pressure late Sunday, saying its inspector general would investigate whether political motivations had tainted the investigation of alleged Russian links to Trump's campaign, which is now being led by special counsel Robert Mueller. "If anyone did infiltrate or surveil participants in a presidential campaign for inappropriate purposes, we need to know about it and take appropriate action," said Deputy Attorney General Rod Rosenstein. Trump's tweet followed reports that an FBI informant had talked to Trump campaign advisers with alleged links to Russia, which the president called a "really big deal" in a tweet Saturday, Politico reports. Analysts described his demand for an investigation of the investigation as unprecedented. "I can't think of a prior example of a sitting president ordering the Justice Department to conduct an investigation like this one," University of Texas School of Law professor Stephen Vladeck tells the New York Times. "That's little more than a transparent effort to undermine an ongoing investigation."