WASHINGTON – Bipartisan lawmakers sounded the alarm Sunday about President Trump’s mounting attacks on the Russia probe and issued a strong defense for special counsel Robert Mueller.

“If the president reaches out and stops this investigation, that is a constitutional crisis in this country,” Sen. Dick Durbin (D-Ill.) said on “Fox News Sunday.”

Trump’s lawyer John Dowd Saturday called for Deputy Attorney General Rod Rosenstein to end the Mueller investigation into Russian meddling in the presidential election and potential collusion with the Trump campaign.

Trump followed up over the weekend by attacking Mueller by name on Twitter and questioning the fairness of his probe.

“If he (Trump) tried to do that, that would be the beginning of the end of his presidency because we are a rule of law nation,” said Republican Sen. Lindsey Graham of South Carolina on CNN’s “State of the Union.”

House Speaker Paul Ryan reiterated his support for the Mueller probe Sunday.

“As the speaker has always said, Mr. Mueller and his team should be able to do their job” Ryan’s spokeswoman AshLee Strong said.

A spokesperson for Senate Majority Leader Mitch McConnell said he stands by his previous statements from January that there’s no need to bring up legislation to protect Mueller from being fired since there’s “no effort underway” by the White House to remove the special counsel.

“I don’t see the need to bring up legislation to protect someone who appears to need no protection,” McConnell said at the time in a statement that still reflects the leader’s thinking.

Republicans on the House Intelligence Committee released a report earlier this month that said its investigation found no evidence of collusion between Trump and the Russians in the 2016 election, but acknowledged it couldn’t interview all the necessary witnesses.

“If you believe, as we found, there is no evidence of collusion, you should want Special Counsel Mueller to take all the time and have the independence he needs to do his job,” said Rep. Trey Gowdy (R-S.C.) on “Fox News Sunday.”

If Trump tries to fire Mueller, Gowdy warned Trump that he would have a hard time getting any replacement confirmed at the Justice Department.

“It’s going to be a very, very long, bad 2018,” Gowdy said. “… If you’ve done nothing wrong, you should want the investigation to be as fulsome and thorough as possible.”

Sen. Jeff Flake (R-Ariz.) said Sunday that firing Mueller is a “massive red line that can’t be crossed.”

On CNN’s “State of the Union” Flake urged Trump: “Don’t go there.”

But White House Director of Legislative Affairs Marc Short downplayed the concerns.

“I’ve not heard a lot of outcry from Republicans,” Short told CBS’ “Face the Nation.” “And all due respect to Jeff Flake, I’m not sure as far as him representing the Republican Party (since) couldn’t get reelected in his own state today.”

Flake is not running for re-election in Arizona, acknowledging his conservative message won’t win in the era of Trump. He’s floated a challenge to Trump in 2020.

Short said everyone in the White House has cooperated with the Mueller probe and “there’s growing frustration” the probe continues.

“I think at some point the American people are owed an answer to say: ‘OK, if there was no collusion, how much longer will this drag on?’” Short said.

The heightened weekend rhetoric reinforced calls for passage of pending legislation to protect Mueller’s probe.

“I would hope that it would prompt all Democrats and Republicans in the House to pass an independent counsel law and reinstate Bob Mueller,” Rep. Adam Schiff (D-Calif.) told ABC’s “This Week.” “This would undoubtedly result in a constitutional crisis and I think Democrats and Republicans need to speak out about this right now.”