During an appearance on Sean Hannity’s Fox News show on Thursday night, Rudy Giuliani, Donald Trump’s legal adviser and cable-news frontman, called on the Justice Department to suspend the special counsel, Robert Mueller, as early as Friday. Giuliani didn’t say whether he had cleared this demand with Trump, but it seems unlikely that he would say such a thing without getting at least some direction, or encouragement, from the President.

In any case, Giuliani’s statement indicates that a moment of crisis may be at hand. For months now, Trump’s closest allies on Capitol Hill and in the news media have been preparing to use a report by Michael Horowitz, the inspector general of the Justice Department, about the F.B.I.’s handling of the 2016 Hillary Clinton e-mail inquiry, as a pretext to go after, and, if possible, derail the Mueller investigation. Just hours after the report was released, Giuliani went on the attack. “I believe Jeff Sessions and Rod Rosenstein have a chance to redeem themselves, and that chance comes about tomorrow,” he told Hannity. “Tomorrow, Mueller should be suspended and honest people should be brought in, impartial people, to investigate these people like Strzok. Strzok should be in jail by the end of next week.”

Strzok is a senior F.B.I. agent who worked on the Clinton e-mail case and the investigation into possible ties between Russia and the Trump campaign. In recent months, Trump and his supporters have seized on some text messages that Strzok sent, in 2016, to Lisa Page, a former employee of the bureau, with whom he was having an affair, as evidence of a “deep state” conspiracy against the President. The inspector general’s report revealed more of these Strzok-Page exchanges, including one, from August of 2016, in which Page said of Trump, he’s “not ever going to become President, right? Right?” Strzok replied, “No. No he won’t. We’ll stop it.”

Clearly, Strzok didn’t like Trump, and when the existence of the texts became public, last year, Mueller removed him from his team. The lengthy inspector general’s report, most of which is devoted to other matters, says that the Strzok-Page texts “potentially indicated or created the appearance that investigative decisions were impacted by bias or improper considerations.” Crucially, however, the report also includes some detailed exculpatory remarks about the duo. (Page resigned from the F.B.I., last month. Strzok is still employed by the agency, but he is facing an internal disciplinary process.)

At one point, the report says, “Our review did not find documentary or testimonial evidence directly connecting the political views these employees expressed in their text messages and instant messages to the investigative decisions we reviewed.” Elsewhere, the report states, in reference to the Clinton e-mail investigation, “We further found evidence that in some instances Strzok and Page advocated for more aggressive investigative measures than did others.”

This finding jibed with the report’s over-all findings. Although the report was highly critical of James Comey, the former director of the F.B.I., for the manner in which he announced that the Clinton e-mail investigation had ended, and later, announced that it had been reopened, it concluded that the investigation itself was carried out professionally and free of political bias. Rather than focussing on that conclusion, which runs counter to what Trump has been saying for almost two years, the President’s supporters, with Giuliani in the lead, are cherry-picking from the report to try to scuttle the Mueller investigation, which didn’t even start until May of 2017, after Trump had fired Comey.

During his interview with Hannity, Giuliani asked how the F.B.I.’s Trump-Russia investigation began, in 2016. Then he answered his own question, by referring to Strzok and Page and claiming, “These people fixed it.” He also said that the Justice Department, once it had suspended Mueller, should “throw out all the people who have been involved in the phony Trump investigation and bring in honest F.B.I. agents from the New York office, who I can trust implicitly. And they should turn their attention to Comey, Strzok, Page.”

To be sure, Giuliani is a loudmouth, and in recent weeks he’s uttered many provocative statements. But in calling on the Justice Department to suspend Mueller and dismantle his investigation, he went beyond anything he has said before. The question now is whether senior G.O.P. politicians, particularly Republican leaders on Capitol Hill, will stand up for Mueller in the face of these incendiary attacks. Unless they do, Trump may well be encouraged to go ahead and order the suspension or firing of Mueller—a course of action that he has clearly been itching to follow for a long time. On Friday morning, he tweeted, “FBI Agent Peter Strzok, who headed the Clinton & Russia investigations, texted to his lover Lisa Page, in the IG Report, that ‘we’ll stop’ candidate Trump from becoming President. Doesn’t get any lower than that!”

On Thursday, Republican statements defending Mueller and the F.B.I. were conspicuously absent. The most vocal responses came from Trump loyalists. In her daily briefing, Sarah Sanders, the White House press secretary, said of the inspector general’s report, “It reaffirmed the President’s suspicions about Comey’s conduct and the political bias among some of the members of the F.B.I.” Ronna McDaniel, the chairwoman of the Republican National Committee, said in a tweet, “The IG report further demonstrates that a fervent anti-Trump bias existed from the very start of the Russia investigation.”

This is the narrative that Trump has been trying to promote for months. What began as a conspiracy theory promoted by the most blinkered Trump loyalists, such as Hannity and Devin Nunes, now has the official imprimatur of the R.N.C. Who, if anybody, in the senior echelons of the Republican Party will stand up for Mueller and the rule of law now? The answer will be clear soon enough.