Yet each of the senators, along with many other participants, had little choice but to address that day’s eruption of Trump news: revelations that he had disclosed classified intelligence about the Islamic State to the Russians during a meeting this month.

“I was prepared to lay out a case today for how President Trump is routinely betraying the working-class voters he pledged to fight for, from his budget to his tax plan to his health care plan and more,” Ms. Gillibrand said. “But last night’s reporting has taken us to a whole new level of abnormal. This is not business as usual.”

Part of the conundrum for the Democrats eyeing the presidency, a roster that may be more than 20 deep, is that they would look out of step with the party base if they did not speak out aggressively against Mr. Trump’s conduct. As demonstrated last week when a series of Democrats competing in statewide primaries called for the president’s impeachment, there is a growing hunger among rank-and-file progressive activists to remove Mr. Trump from office.

To ultimately be on the wrong side after that litmus test could prove dangerous in a nomination fight.

But the obsessions of the most intense partisans have not fully resonated with the broader electorate. Asked whether they approved of Mr. Trump’s decision to fire James B. Comey as director of the F.B.I. — the news equivalent of a four-alarm fire in Washington — 32 percent of voters in an NBC News-Wall Street Journal poll this month responded that they did not know enough to say. That figure was about halfway between the percentage of people who said they supported the firing and those who opposed the move.

“There’s this Washington narrative, and then there’s a voter narrative,” said Anita Dunn, a longtime Democratic strategist. “Significant parts of our base are following the Washington narrative very closely, but for voters who voted for Donald Trump or voters who didn’t vote at all, I think Democratic candidates are going to have to make the election meaningful to those voters’ lives.”