Last July, John Brennan, then the head of the C.I.A., sat underneath an enormous white tent in Aspen, Colorado, and sketched a dire picture of what awaited the next President. Brennan told the audience at the annual Aspen Security Forum that the United States faced the most complex set of threats that he had seen in his thirty-six-year intelligence career, ranging from unprecedented cyberattacks, to a metastasizing ISIS, to an increasingly assertive Russia and China. During his own question-and-answer session at the forum, James Clapper, then the director of national intelligence, delivered a similarly grim assessment.

On Friday, Brennan and Clapper returned to the forum, an annual gathering held by the Aspen Institute far from Washington to foster bipartisan consensus regarding national security. Sitting shoulder to shoulder onstage, the two former intelligence chiefs unleashed a blistering and highly unusual public critique of a sitting President by two former intelligence chiefs. Brennan urged members of Congress to resist President Trump if he fires Robert Mueller, the special counsel. “I hope, I really hope, that our members of Congress, elected representatives, are going to stand up and say, ‘enough is enough,’ and stop making apologies and excuses for things that are happening that really flout, I think, our system of laws and government.”

Brennan added that he thought it was “the obligation of some executive-branch officials to refuse to carry out some of these orders that, again, are inconsistent with what this country is all about.”

Both men assailed Trump for accusing U.S. intelligence agencies of leaking stories to the press that Russia had compromising information about him and saying “that’s something that Nazi Germany would have done and did do.” Clapper called Trump’s comparison of U.S. intelligence agencies to the Nazis “a terrible, insulting affront” that was “completely inappropriate and over-the-top.” Brennan said Trump’s comments were “just disgraceful, never should have happened,” and “the person who said that should be ashamed of himself.”

The two men pilloried Trump’s statement to Russian President Vladimir Putin at a recent G-20 summit in Germany that it was “an honor” to meet him and questioned Trump’s hour-long dinner conversation with Putin and a Russian-government translator. The presence of no American translator was “very dangerous,” and the two leaders could “completely miscommunicate,” Clapper said.

Brennan said the presence of no other American officials made it possible for Trump to lie about the conversation. “Quite frankly, I think there are concerns that sometimes what Mr. Trump says happens is not exactly what happens,” Brennan said. “I think it just raises again concerns about what else may be going on between Mr. Trump and Mr. Putin that is being held behind either closed doors or outside of public view.”

Brennan ended the hour-long question-and-answer session, moderated by the CNN anchor Wolf Blitzer, with a rousing call for attendees to defend press freedom in the Unites States, prompting a standing ovation from the audience.

But immediately after Brennan and Clapper spoke, on the very same stage, two top congressional Republicans made it clear that they are not ready to break with Trump. Under questioning from Ryan Lizza, of The New Yorker, Representative Michael McCaul, the chairman of the House Committee on Homeland Security, and Representative Mac Thornberry, the chairman of the House Armed Services Committee, both declined to say that Trump’s firing of Mueller would be a “red line” that the President should not cross. McCaul backtracked on a statement he made earlier in the day to NBC news that the firing of Mueller would spark a “tremendous backlash” in Congress. Instead, he said that if Trump fired Mueller it would not be “received well” because of the respect both Democrats and Republicans have for Mueller. Thornberry said he did not want to comment on hypothetical situations.

McCaul also declined to criticize Donald Trump, Jr., for meeting with what he had been told was a Russian lawyer offering damaging information on Hillary Clinton from the Russian government. Asked if he would attend such a meeting, McCaul gave a convoluted answer, first saying “it’s a tough question” because “you obviously want to know all the information out there.” He then said he would not do so because meeting with a foreign adversary creates a legal issue and a “political optics issue.” He then questioned whether Donald Trump, Jr., was “sort of duped by the Russians or was this more of a collusion-type event.” Thornberry said he would decline the meeting and call the F.B.I., and he said he was “like Clapper” and did not trust the Russians. But Thornberry said he worried that the “drama” surrounding the Trump-Russia investigation was distracting the U.S. government from addressing the long-term Russian national-security threat.

In the final event of the day, the current director of national intelligence, the Republican former Senator Dan Coats, of Indiana, said morale was high in the intelligence community under Trump. During a question-and-answer session, Julia Ioffe of The Atlantic asked Coats about a breaking story from the Washington Post that communications intercepts obtained by U.S. intelligence agencies contradict Attorney General Jeff Sessions’s descriptions of his meetings with the Sergey Kislyak, the Russian Ambassador to the U.S., during the 2016 campaign. In a seeming rejoinder to Brennan’s defense of the press, Coats dismissed the story.

“I've come to the point where I no longer put any stock in headlines or breaking news,” Coats said. “I'm going to ask, you know, is this for real, is this the real thing, try to get some details before I draw a conclusion.”

Coats’s disparagement of the story prompted applause from audience members, just as Brennan’s praise of the press did. In conversations with current and former intelligence officials at the forum, I encountered similar whiplash. Some expressed anger and alarm regarding Trump and Russia. Others said Democrats were hyping the investigation. Current officials said the intelligence community was as diverse politically as the American public and neither overwhelmingly pro-Trump nor anti-Trump. Over all, the Trump-Russia investigation hung over the conference. There was scant sense of consensus at a forum designed to foster it and an undercurrent of anxiety, uncertainty, and worry.

Trump defenders and opponents agreed on one point. The unprecedented array of threats described by Brennan and Clapper last year in Aspen are growing worse. But the ceaseless drumbeat of Trump-Russia disclosures is paralyzing Washington’s ability to respond to them.