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 By Tom Winter 
 
 The longtime chief financial officer of the Trump Organization, Allen Weisselberg, was given immunity by federal prosecutors in New York during the course of the Michael Cohen investigation, according to two people with knowledge of the matter. 
 
 The news was first reported Friday by The Wall Street Journal. 
 
 Weisselberg is "Executive 1" on page 17 of the criminal information filed by prosecutors in the Michael Cohen case, a person with knowledge of the matter told NBC News. 
 
 According to prosecutors, Cohen, then Trump's attorney, sent an invoice to Executive 1, meaning Weisselberg, for "Payment for services rendered for the month of January and February, 2017," a payment that was really meant to reimburse Cohen for a payment to Stormy Daniels. 
 
 Weisselberg then sent the invoice to another Trump Organization executive via e-mail directing him to "Please pay from the Trust. Post to legal expenses. Put 'retainer for the months of January and February 2017' in the description." 
 
 A spokesperson for the U.S. Attorney's Office for the Southern District of New York declined comment. 
 
 Weisselberg, 70, began working for the Trump Organization as an accountant in the 1970s, when President Donald Trump's father, Fred, ran the company. Weisselberg was also treasurer of the Donald J. Trump Foundation, the president's charitable organization, which has been sued by the New York attorney general for alleged violations of state law. 
 
 Cohen mentioned Weisselberg's name several times on a recorded phone conversation with Trump about a payment to kill a story about Trump's alleged relationship with Playboy model Karen McDougal. The tape was seized during the FBI's April raid on Cohen's residence and office, and was released to the media by Cohen's attorney, Lanny Davis. 
 
 On the tape, recorded two months before the 2016 presidential election, Cohen mentions that he has spoken to Weisselberg about setting up a corporation to process the payment. 
 
 "I need to open up a company for the transfer of all that info regarding our friend David," says Cohen, "so that — I'm going to do that right away. I have spoken to Allen Weisselberg about how to set the whole thing up with funding." 
 
 "David" is apparently David Pecker, a Trump friend who is the chairman and CEO of American Media and publisher of the National Enquirer, which had agreed to purchase McDougal's story. ||||| The greatest threat to President Trump is not the investigation by special counsel Robert Mueller but other probes by U.S. prosecutors in New York, said Alan Dershowitz, a Harvard Law School professor emeritus. 
 
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 Dershowitz told ABC News Chief Anchor George Stephanopoulos on "This Week" Sunday that the biggest legal danger to the president is from an investigation by the Southern District of New York in Manhattan. 
 
 Federal prosecutors in New York are investigating whether the Trump Organization was involved in campaign finance violations connected to former Trump lawyer Michael Cohen. In connection to that probe, they have granted immunity to the Trump company’s chief financial officer, Allen Weisselberg. 
 
 “I think [Trump] has constitutional defenses to the investigation being conducted by Mueller,” into Russian interference in the 2016 election, said Dershowitz, who is author of the book, "The Case Against Impeaching Trump." 
 
 “But there are no constitutional defenses to what the Southern District is investigating,” the legal scholar said. "I think the Southern District is the greatest threat." 
 
 John Lamparski/Getty Images, FILE 
 
 "Last week proves ... that the special counsel is the least important element in this investigation” into the president and the 2016 campaign, Dershowitz added, referring to former Trump lawyer Michael Cohen's pleading guilty in New York on Tuesday to tax evasion and campaign finance violations. 
 
 Cohen admitted in his plea to arranging hush money agreements for two women, Stormy Daniels and Karen McDougal, who allege they had affairs with Trump prior to the November 2016 election. The president has denied both women’s allegations. 
 
 Cohen also said in court that he made those payments "in coordination and at the direction of a candidate for federal office,” whom his attorney later identified as Trump. 
 
 Federal prosecutors in New York are considering possible charges against the Trump Organization in relation to the Cohen hush-money agreement with Daniels, an official briefed confirmed to ABC News on Friday. No charges were imminent. 
 
 Nicholas Kamm/AFP/Getty Images 
 
 Separately, federal prosecutors in New York granted immunity to tabloid executive and longtime Trump friend David Pecker to discuss Cohen’s case. And the Trump Organization's Weisselberg has also been granted immunity in exchange for cooperation with the Cohen investigation. 
 
 Dershowitz on Sunday also commented on the possibility that Trump could replace Attorney General Jeff Sessions. The president has increased his attacks on Sessions, including over the attorney general's recusing himself from overseeing the Mueller investigation. 
 
 Dershowitz said that while Trump has the right to fire Sessions, “I think it would be a mistake to fire anybody.” 
 
 “My advice to the president, I never gave it to him privately because I’m not his lawyer, but on television is, 'Don’t fire, don’t pardon, don’t tweet and don’t testify,'” Dershowitz said on "This Week." 
 
 As to Dershowitz’s reference to the president’s constitutional protections in the Mueller probe, the special counsel wants to speak to Trump about obstruction of justice, sources have told ABC News. 
 
 Trump’s public attacks on Sessions and Mueller and his firing of former FBI Director James Comey have raised questions as to whether the president could be engaging in obstruction of justice in regard to the special counsel probe. 
 
 Dershowitz maintains that a president has the right to fire people in the executive branch and that his possible motives for taking such actions can’t be subject to criminal investigation, according to an excerpt from his book published in The Forward. 
 
 "A president cannot be charged with obstruction of justice for merely exercising his power” under the Constitution, Dershowitz said in a prior appearance on “This Week.”
– First Michael Cohen, then David Pecker, and now Allen Weisselberg. Another longtime ally of President Trump has been granted immunity by prosecutors in exchange for testimony. The 70-year-old Weisselberg is no mere acquaintance: He has served for decades as chief financial officer and executive VP of the Trump Organization, reports the Wall Street Journal. In fact, when Trump was elected president, he turned over the financial reins of his business empire to Weisselberg and to Trump's adult sons. Weisselberg actually started working for the organization in the 1970s, when Trump's father, Fred, ran it, per NBC News. Earlier this year, Weisselberg was called to testify before a grand jury as part of the investigation of Cohen's payments to two women in exchange for their silence about alleged affairs with Trump. Weisselberg had been mentioned in a recorded conversation between Cohen and Trump about how to facilitate a payment to former Playboy model Karen McDougal. Cohen has pleaded guilty to eight charges and said Trump directed him to make the hush-money payments ahead of the election, possibly implicating the president in a federal crime. It's not clear what information Weisselberg provided in the investigation. (This week, Trump suggested that "flipping" in exchange for deals with prosecutors should be illegal.)