As Donald Trump’s public castigations of Jeff Sessions have intensified over the past week amid reports that the president might fire the embattled attorney general, possibly as part of a broader strategy to oust special counsel Robert Mueller, the underpinnings of Trump’s version of the “Saturday Night Massacre” have come into focus. And as it was with Richard Nixon, the question for Trump is not so much what is permissible under the law, but what such a stroke might awaken. “Sometimes the least important questions here are the ones about legality and the most important questions about the political dynamics,” Josh Chafetz, a constitutional law professor at Cornell Law School, told me. “It’s not about what is the best reading of law, so much as it is—what is going to cross the line, especially for Republicans in Congress? That’s what we need to figure out and we may not know the answer to that until it is crossed, if it ever is.”

Trump’s attacks on Sessions began last week when, during an interview with The New York Times, he said that he never would have appointed the Alabama senator to head the Justice Department if he had known that he would recuse himself from matters related to Russia’s interference in the presidential election. In the days since, he has fired off a series of tweets attacking the “beleaguered” top lawyer for his “VERY weak position on Hillary Clinton crimes” and for not stemming the deluge of intelligence leaks. “It’s not like a great loyal thing about the endorsement . . . I’m very disappointed in Jeff Sessions,” Trump said in an interview with the Wall Street Journal. “If Jeff Sessions didn’t recuse himself, we wouldn’t even be talking about this subject,” he continued, referring to the ongoing F.B.I. investigation. When asked whether he would fire Sessions, Trump demurred. “I’m just looking at it . . . I’ll just see. It is a very important thing.”

A number of Republican senators publicly announced their support for Sessions—though most stopped short of full-throated criticism of Trump, taking the tack of defending their colleague of 20 years rather than rebuking the president. Oklahoma Senator James Inhofe said “I’m 100 percent for the president, but I really have a hard time with this.” Orrin Hatch said of Trump, “I’d prefer that he didn’t do that. We’d like Jeff to be treated fairly.” Thom Tillis of North Carolina said, “I guess we all have our communication style and that is one that I would avoid,” and added that Sessions’s showing independence from the president is “a healthy thing.” Lindsey Graham went furthest, writing on Twitter that Trump’s suggestion that Sessions should “pursue prosecution of a former political rival is highly inappropriate.”

But House Speaker Paul Ryan poured water on the burgeoning constitutional crisis, at least for now. “The president gets to decide what his personnel is, you all know that. He’s the executive branch. We’re the legislative branch. He determines who is hired and fired in the executive branch—that’s his prerogative,” the Wisconsin lawmaker said. “If he has any concerns or questions or problems with the attorney general, I’m sure he’ll bring it up with him himself.”

Ryan isn’t wrong that a president has the authority to dismiss his attorney general, but the net response from Republican lawmakers to Trump’s threat, arguably, reads like an invitation to fire Sessions. “There are informal ways, members of Congress can communicate to the president that they won’t support him if he does this, that there will be a much more definitive break then there has been,” Louis Michael Seidman, a constitutional law professor at Georgetown University, told me. “There are ways around the formal checks, but I think the informal checks are more important. Republicans on the Hill can signal to him that there are limits to what they are willing to accept. Now whether they do that or not, it’s anybody’s guess.”