Republican Sen. Lindsey Graham (R-SC) is taking a hard line on the Russia investigation and the president’s seeming inability to stay out of it. On Sunday, Graham warned that Firing Robert Mueller, the special counsel investigating the Russia scandal, would be the end of the Donald Trump presidency — adding that everyone surrounding the president knows it.

“It’s pretty clear to me that everybody in the White House knows it would be the end of President Trump’s presidency if he fired Mr. Mueller,” Graham told ABC’s Martha Raddatz in an appearance on This Week on Sunday. The remarks come amid revelations that Trump ordered Mueller’s firing last June, reported by the New York Times this week and subsequently confirmed by other outlets, including the Washington Post and CNN.

Top White House lawyer Don McGahn threatened to quit instead of going through with the president’s order, which apparently stopped the president from going through with it. The report provides another example of President Trump’s attempts to interfere with ongoing investigations — a pattern of behavior that has put him under scrutiny for potential obstruction of justice.

Graham said he didn’t know whether the stories about Trump’s order to fire Mueller or McGahn’s threat to quit stopping him were true, despite them being confirmed by multiple reputable news outlets (and, oddly enough, by Sean Hannity), but said he believes Mueller should look into it. “We’re not just going to say it’s fake news and move on. Mueller is the best person to look at it,” he said. He clarified he sees no evidence Trump wants to fire Mueller now.

Does Sen @LindseyGrahamSC still trust the Mueller investigation? “As a matter of fact, I think Mr. Mueller is the perfect guy to get to the bottom of all this, and he will.” #ThisWeek pic.twitter.com/QjglilKSW6 — This Week (@ThisWeekABC) January 28, 2018

Graham was among a group of both Republican and Democratic senators last summer to introduce legislation seeking to block Trump from firing Mueller. He co-sponsored a bill with Democratic Sen. Cory Booker (D-NJ). A similar measure was introduced by Sens. Thom Tillis (R-NC) and Chris Coons (D-DE) around the same time.

On Sunday, Graham said he’d be “glad to pass it tomorrow” but clarified that he thinks “it would be good to have legislation protecting all special counsels.” He also called for a special counsel to probe the Department of Justice and the FBI’s handling of the Hillary Clinton email investigation and the early stages of the Russian investigation — seemingly toeing a line in an attempt not to anger the president or other Republicans.

Many lawmakers remain lukewarm on Trump potentially firing Mueller

Graham largely stands alone in the GOP in the forcefulness of his rhetoric on the Russia investigation and his commitment to protecting Mueller.

In an appearance on CNN’s State of the Union with Jake Tapper on Sunday, Republican Sen. Susan Collins (R-ME) said it “probably wouldn’t hurt” to pass one of the proposed bills to block the president from firing Mueller. Collins, widely considered one of the party’s most moderate lawmakers, said enshrining that protection in law isn’t a bad idea. “There are some constitutional issues with those bills, but it would certainly not hurt to put that extra safeguard in place, given the latest stories,” she said.

House Majority Leader Kevin McCarthy (R-CA) disagreed, saying he still just can’t see why such legislation would be necessary. “I don’t think there’s a need for legislation right now to protect Mueller,” he said In an interview with NBC’s Chuck Todd on Meet the Press. “So we’re raising an issue that’s not.”

EXCLUSIVE: @GOPLeader Rep. Kevin McCarthy (R-Calif.) on #MTP this morning says, "I don't think there's a need for legislation right now to protect Mueller." pic.twitter.com/iKTOIlfNDb — Meet the Press (@MeetThePress) January 28, 2018

Democratic Sen. Joe Manchin (D-WV), who is up for reelection in 2018 and is one of the party’s more moderate members, told NBC’s Todd on Sunday that Trump’s order to fire Mueller was probably just “New York talk” — sort of taking a line from Trump’s “locker room talk” excuse over the Access Hollywood tape.

When pressed on the assertion by Todd, he went on to discuss Trump’s business record and explain that that’s probably why Trump thought it would be a good idea to cut Mueller. “You have a person who’s the president of the United States that has been totally in control of his life, personally and professionally,” he said. “Now all of a sudden he’s understanding there’s equal branches and there’s equal powers.”

Manchin said if Trump fires Deputy Attorney General Rod Rosenstein, the person who actually has the authority to fire Mueller, that’s when he’d start to worry.

Whether Trump firing Mueller would actually lead to any consequences is, at the very least, unclear — Republican lawmakers aren’t exactly chomping at the bit to really go after the president. Their latest comments on the matter aren’t exactly heartening.