Will President Donald Trump and his Republican allies in Congress let special counsel Robert Mueller complete the Russia investigation? That’s long been a legitimate, unanswered question in Washington. Over the weekend, the balance of probability leaned toward “no,” as a constitutional crisis looks likelier by the day.

It began late Friday night when Attorney General Jeff Sessions announced he had fired former FBI Deputy Director Andrew McCabe, citing an alleged lack of candor by McCabe when speaking to internal investigators about his role in the bureau’s activities during the 2016 election. McCabe immediately shot back at the accusations.

“This attack on my credibility is one part of a larger effort not just to slander me personally, but to taint the FBI, law enforcement, and intelligence professionals more generally,” he said in the statement. “It is part of this Administration’s ongoing war on the FBI and the efforts of the Special Counsel investigation, which continue to this day. Their persistence in this campaign only highlights the importance of the Special Counsel’s work.”

It’s hard to weigh the claims against McCabe without reading the Justice Department inspector general’s report, which is expected to be released some time in the coming weeks. In practical terms, his ouster doesn’t affect the course of the Russia investigation. McCabe had already stepped aside from his post in January at the behest of FBI Director Chris Wray. Since then, he’s been in a professional limbo of sorts, remaining on the FBI payroll so he could retire with his full pension on Sunday.

What’s known without the inspector general’s report, though, is that the president has waged a sustained public campaign against McCabe, attacking his credibility and pressuring Sessions into firing him. Shortly after McCabe’s ouster became public, the president struck a triumphal note on Twitter. “Andrew McCabe FIRED, a great day for the hard working men and women of the FBI - A great day for Democracy,” Trump wrote. He then linked McCabe’s dismissal to that of James Comey, whom Trump fired as FBI director last year. “Sanctimonious James Comey was his boss and made McCabe look like a choirboy,” he added. “He knew all about the lies and corruption going on at the highest levels of the FBI!”

Then the president kept tweeting. On Saturday morning, he cited the House Intelligence Committee’s disputed report claiming their investigators had found no evidence of collusion between the Trump campaign and the Russian government. He revived a dubious right-wing talking point that McCabe acted inappropriately because of campaign donations his wife received when she ran for a state senate seat in Virginia. Finally, he took direct aim at Mueller for the first time.

“The Mueller probe should never have been started in that there was no collusion and there was no crime,” he wrote. “It was based on fraudulent activities and a Fake Dossier paid for by Crooked Hillary and the DNC, and improperly used in FISA COURT for surveillance of my campaign. WITCH HUNT!”

The tweet’s claims are largely erroneous. Nonetheless, it ended a rare example of self-restraint by a largely unrestrained president. For months, Trump avoided calling out Mueller by name even as he lashed out at the Russia investigation in public and attempted to fire the special counsel in private. This strategic silence apparently came from warnings by his advisers and legal team that directly attacking the special counsel would only make things worse.

Now, even some of his lawyers have changed their tune. John Dowd, one of Trump’s attorneys, told The Daily Beast on Saturday that he hoped Deputy Attorney General Rod Rosenstein “will follow the brilliant and courageous example of the FBI Office of Professional Responsibility and Attorney General Jeff Sessions and bring an end to alleged Russia Collusion investigation.” Ty Cobb, one of the president’s other attorneys, denied on Sunday that anyone in the White House was discussing Mueller’s removal, but the bell couldn’t be unrung.

Amid this growing campaign against Mueller and the Justice Department’s independence, congressional Republicans largely stayed silent over the weekend. The attacks on Mueller drew scorn from the president’s most frequent GOP critics, like Arizona Senators John McCain and Jeff Flake. South Carolina Senator Lindsey Graham also repeated his past assertion that removing Mueller “would be the beginning of the end of his presidency, because we’re a rule-of-law nation.”

But most Republicans said nothing. House Speaker Paul Ryan issued a tepid statement asserting that “Mr. Mueller and his team should be able to do their job,” without mentioning Trump, while Senate Majority Leader Mitch McConnell made no public comment. Steve Scalise, the House Republicans’ third-in-command, instead suggested that there are “credibility concerns the Mueller investigation needs to address so they can dispel the fears that this is becoming a partisan witch hunt.”

At this point, it appears anything but silence or muted criticism will encourage the president to be more aggressive. It’s been a turbulent few weeks for Trump already: He fired Secretary of State Rex Tillerson via Twitter, and The New York Times reported that other Cabinet members and top West Wing officials may be on the chopping block—including Attorney General Jeff Sessions, a former political ally whom Trump turned against for recusing himself from the Russia investigation last year.

If Trump fires Sessions and puts a new attorney general in place, he or she wouldn’t be recused from the Russia probe and would supersede Rosenstein in overseeing Mueller’s investigation. (It’s not assured that the Senate would confirm Trump’s next nominee for attorney general, but there might be a statutory way to put other Senate-confirmed officials atop the Justice Department temporarily.) Mueller is independent in his day-to-day functions, but still requires approval from the attorney general or acting attorney general for major investigative decisions. With the right pick, Trump would have an opportunity to indirectly rein in the special counsel or shut him down entirely.

Congressional Republicans have made that possibility more likely by staying silent. A healthy share of the blame goes to California Representative Devin Nunes, who politicized the House Intelligence Committee and issued a half-baked report in an effort to exonerate the president. But plenty of it can also be spread among the GOP legislators who refuse to challenge the president more directly or at all, as a co-equal branch of government is supposed to do.

Trump would bear ultimate responsibility for shutting down or curtailing the Russia investigation, of course. But if it happens, no one can say he acted alone.