(Reuters) - President Donald Trump could trigger a political and legal backlash if he escalates his attacks on Attorney General Jeff Sessions into an attempted purge of U.S. law enforcement officials, lawmakers and legal experts said on Tuesday. In lashing out against an investigation of possible ties between his 2016 campaign and Russia, Trump is slamming Sessions, prompting speculation that the president wants to oust the attorney general.[nL1N1KG11O] If Robert Mueller, the special counsel running the Russia investigation, is Trump’s ultimate target and he moves to fire Mueller, a legal and political showdown could ensue. Senator Angus King, an independent from Maine, told CNN on Tuesday that he expected fellow lawmakers would not tolerate any effort by Trump to replace Sessions with a loyalist, especially if it appeared aimed at undermining Mueller’s investigation. “The senators are going to be very skeptical about this,” said King, who normally votes with Democrats. “My expectation is you’d see a special prosecutor pass by veto-proof majorities in both houses. And the investigation would continue.” Trump, who dismissed James Comey as director of the Federal Bureau of Investigation as it was looking into possible Russian connections, was asked about Sessions at a news conference on Tuesday and said, “Time will tell. Time will tell.” These remarks followed Twitter messages by Trump in which he described Sessions as “weak” and “beleaguered.” Senate Republican leader Mitch McConnell told reporters in a Capitol hallway on Tuesday that Sessions is “doing a fine job.” Republican Richard Shelby told reporters Sessions, formerly his fellow senator from Alabama, is “not the president’s lawyer; he is the attorney general of the United States.” Here are basics on the law covering dismissal of Justice Department officials, including Mueller, who was appointed by Deputy Attorney General Rod Rosenstein because Sessions is recused from matters dealing with the Russia investigation. On what grounds could Mueller be fired? Justice Department regulations say a special counsel can only be removed for “misconduct, dereliction of duty, incapacity, conflict of interest, or for any other good cause.” Do Trump’s claims that Mueller is on a “witch hunt” and that he is conflicted constitute “good cause?”   Probably not. No court has ever interpreted the meaning of “good cause” in this context. But Mueller has a sterling reputation and there is no indication he has exceeded the scope of his mandate, said Andrew Wright, former associate counsel in the Obama White House and professor at Savannah Law School. Campaign donations from members of Mueller’s team to Democrats do not pose a conflict of interest, Wright said. Could Trump directly fire Mueller?     Probably not. Department of Justice rules say the special counsel can only be fired by the attorney general or the acting attorney general. Trump has criticized Rosenstein for appointing Mueller and due to Session’s recusal, Rosenstein has sole authority to fire Mueller. But a few constitutional lawyers have said that Trump might be able to lawfully fire Mueller directly. Saikrishna Prakash of the University of Virginia Law School said the special counsel regulations may interfere with the president’s broad power under the Constitution to remove executive branch officials. “I don’t know if that regulation is constitutional,” he said. If Trump fires Sessions or Sessions quits, could Trump handpick an attorney general who would fire Mueller? Normally, the president nominates an attorney general who must win Senate confirmation. If Trump followed this course, the Senate would likely press any nominee on his or her intentions on terminating Mueller, Prakash said.  “The Senate is going to want promises that this person will be independent of the White House and not be a toady,” he said.  How else could Trump name an attorney general who he believes would fire Mueller? Under the Federal Vacancies Reform Act of 1998, Trump could appoint an interim attorney general, but only someone previously confirmed by the Senate. The law can only be invoked to replace officials who die, resign or are “otherwise unable” to do their job. If Trump invoked the Federal Vacancies Reform Act to replace Sessions, a court may rule that Trump overstepped, Josh Chafetz, a professor of constitutional law at Cornell Law School, said. What about a recess appointment?  Trump could try replacing Sessions while the Senate is on summer recess, expected to begin Aug. 11. The constitution grants the president such authority, said Stephen Vladeck, constitutional law professor at the University of Texas School of Law.      The Supreme Court ruled in 2014 the president cannot make a recess appointment during recesses of less than 10 days. The Senate calendar is controlled by Trump’s fellow Republicans.      Senate Democratic leader Chuck Schumer said on Tuesday that Democrats would use every tool at their disposal to block a recess appointment of a Sessions replacement. If Mueller were fired, could he mount a court challenge? Unclear. Vladeck said the special counsel regulations do not address this question. If he brought a lawsuit, Mueller likely would argue the rules would be pointless if there was no way to enforce them, Vladeck said. 
Impact of firing Sessions could be troublesome for Trump