(CNN)Republican Sen. Jeff Flake, an outspoken critic of President Donald Trump, tweeted Tuesday that if the President were to fire special counsel Robert Mueller, the "only constitutional remedy is after the fact, through impeachment."
"We are begging the president not to fire the special counsel," tweeted the Arizona Republican, who is not running for reelection. "Don't create a constitutional crisis. Congress cannot preempt such a firing. Our only constitutional remedy is after the fact, through impeachment. No one wants that outcome. Mr. President, please don't go there."
Concerns about the President potentially firing the special counsel grew over the weekend after Trump criticized Mueller by name on Twitter and his lawyer said he prayed for an end to the investigation into Russian meddling and possible collusion between the Trump campaign and Russian officials.
Flake, who sits on the Senate Judiciary Committee, has been hesitant this week whether to back existing legislation that would protect the special counsel from political pressure at the White House, saying there were some constitutional questions about the legislation.
His tweet Tuesday indicated that he doesn't believe Congress could legislate a law that would protect the special counsel.
"It needs to be constitutional, and we're trying to explore that. I'm not convinced that's what's been introduced so far is constitutional," Flake told reporters on Monday.
The White House has repeatedly denied this week that Trump is considering the ouster of Mueller.
"The President is not considering or discussing the firing of special counsel Robert Mueller," White House spokeswoman Sarah Sanders said Tuesday.
Senate Majority Leader Mitch McConnell forcefully defended Mueller Tuesday saying the should be allowed to finish his investigation and that legislation was "not necessary" to shield him.
"I agree with the President's lawyers that Bob Mueller ought to be allowed to finish his job. I think he was an excellent appointment," McConnell told reporters at his weekly news conference in the Capitol. "I think he will go wherever the facts lead him and I think he will have great credibility with the American people when he reaches the conclusion of his investigation. So, I have a lot of confidence in him."
In an interview with The Washington Post, Flake compared the potential firing to when President Richard Nixon fired the special prosecutor investigating the Watergate controversy.
"If (Trump) fires (Mueller) without cause, how different is that from what Nixon did with the 'Saturday Night Massacre'?" Flake asked. "He left before impeachment came, but that was the remedy then and that would be the remedy now."
