WASHINGTON — High-profile supporters of President Donald Trump are turning on special counsel Robert Mueller, the man charged with investigating Russian interference in the U.S. election and possible collusion with Trump’s campaign.

As Mueller builds his legal team, Trump’s allies have begun raising questions about the former FBI director’s impartiality, suggesting he cannot be trusted to lead the probe. The comments come amid increasing frustration at the White House and among Trump supporters that the investigation will overshadow the president’s agenda for months to come — a prospect that has Democrats salivating.

Trump friend Chris Ruddy, the CEO of Newsmax, went so far as to suggest the president was already thinking about “terminating” Mueller from his position as special counsel.

“I think he’s considering perhaps terminating the special counsel,” Ruddy said in an interview with Judy Woodruff of “PBS NewsHour.” “I think he’s weighing that option.”

Under current Justice Department regulations, firing Mueller would have to be done by deputy attorney general Rod Rosenstein, not the president — though those regulations could theoretically be set aside.

Rosenstein may be asked to address the issue when he speaks at a Senate subcommittee hearing this morning.

Attorney General Jeff Sessions recused himself from all matters having to do with the Trump-Russia investigation because of his own conversations with Russian officials during the Trump transition.

Former House Speaker Newt Gingrich, an informal Trump adviser, tweeted Monday, “Republicans are delusional if they think the special counsel is going to be fair. Look who he is hiring.”

Just weeks ago, Gingrich had heaped praise on Mueller, hailing him as a “superb choice” for special counsel whose reputation was “impeccable for honesty and integrity.”

But after the testimony of former FBI Director James Comey last week, Gingrich said he’d changed his mind.

“Time to rethink,” he tweeted Monday, citing Mueller’s hiring decisions and Comey’s admission that he’d instructed a friend to share with reporters notes he’d taken of his private conversations with Trump in order to force the appointment of a special counsel.