By mid-February, spirits in Democratic Washington had palpably lifted. You wouldn’t have described the mood as triumphal; it was more as if everyone had emerged from the basement after a tornado to discover that, while the car was upside down somewhere, at least the house was still standing. The travel ban remained marooned, at least temporarily, in the courts. (A redrafted executive order was issued on March 6, but it was unclear if it had fully resolved the legal issues of the first.) Trump’s nominee for labor secretary, the fast-food C.E.O. Andrew Puzder, backed out of consideration for the job in mid-February after the Republicans concluded that they did not have the votes to confirm him. The project of doing away with the Affordable Care Act was still tied up in committee amid disagreements among the Republicans themselves — an inevitable consequence, perhaps, of their eight-year all-or-nothing opposition effort that the Democrats were now studying. And the infrastructure bill that had threatened to divide Democrats against themselves never materialized; there was talk now of it being pushed back to 2018.

On Feb. 28, a few hours before Trump was due to give his first speech to Congress, I went to see Schumer in the minority leader’s chambers in the Capitol. The senator was sitting in a leather wingback chair in his shirt sleeves, and he seemed to be in a genuinely upbeat mood. “Things look much better for us and much worse for him than I ever imagined based on the first month,” he told me. The day before, three Republican senators — Ted Cruz, Mike Lee and Rand Paul — had held out for nothing less than full repeal of the Affordable Care Act. “That’s the three votes they need, even with 52!” Schumer crowed. (The following week, a replacement bill finally began to advance through committees in the House of Representatives, but Paul declared in a Fox News interview that it would be “dead on arrival” in the Senate.) He pointed to the crowds that Indivisible and other groups had turned out in the thousands at town halls across the country the previous week. “Trump is the enemy, and his Republican acolytes — not Democrats,” he said. “We’re already beginning to coalesce around that. It was very positive. They throw a few brickbats, fine. This energy is enormous.”

But even as a sort of guarded optimism set in among many Democrats, there was a gloom among the party’s left flank that appeared nearly as thick as it was in November — a sense that the party, buoyed by the easy gratification of opposition, was punting on resolving difficult questions, at its own peril. Just before visiting Schumer, I went to see Bernie Sanders in his Capitol Hill office. In a couple of hours, the Vermont senator’s colleagues would be gathering in Senate dining room to share a meal — a bipartisan tradition before presidential speeches to Congress. But Sanders did not intend to be among them. “I think I’m going to skip the dinner tonight,” he said. “I’m not in a very convivial mood. I don’t want to pretend. These are very, to my mind, frightening times.”

Since ending his presidential campaign in July, Sanders, who caucuses with the Democrats in the Senate, had been managing the complicated task of redirecting the movement that materialized around his candidacy toward a Democratic Party with which he had a tetchy relationship. Schumer had created a post for him in the party’s Senate leadership, and Sanders had helped mobilize his grass-roots network for two rounds of rallies in defense of the Affordable Care Act. But earlier in the week, he said in a CNN interview that “a total transformation of the Democratic Party” was still in order, and that he had also not yet given the D.N.C. — which he called the “establishment’s house” — access to his campaign email list. “It’s not some magical system,” Sanders told me, disdain dripping off the word “magical.” “How do we bring in, how do you raise money from, those people? You know what? You’ve got to stand for something.”

I asked him if he thought the Democratic Party knew what it stood for. “You’re asking a good question, and I can’t give you a definitive answer,” he said. “Certainly there are some people in the Democratic Party who want to maintain the status quo. They would rather go down with the Titanic so long as they have first-class seats.”

In early February, Elizabeth Warren, in a speech to the Congressional Progressive Caucus, warned that while the Democrats were fashioning themselves into an opposition party, that was not enough to solve the problems that put them in the position of becoming an opposition party in the first place. “Men like Donald Trump come to power when their countries are already in deep trouble,” she said. “There are some in the Democratic Party who urge caution. They say this is a tactical problem: ‘We need better data. We need better social media. We need better outreach. We need better talking points.’ Better talking points? Are you kidding me? People were so desperate for economic change in this country that Donald Trump was just inaugurated as president, and people think we need better talking points? What alternative planet are they living on?”

When I met Warren a few weeks later, I asked her about the speech, and whether the postelection unity that Trump provided the Democratic Party made her ambitions to reform it easier or harder to realize. “I think it has reminded Democrats we need to run on our values,” she replied, parrying the question. “Because our values are more in line with most of America.” If you squinted at the bodies packing the streets and the town halls, though, the picture looked an awful lot like the recent past: Here were people drawn together in defense of liberal immigration and refugee policies, reproductive rights, civil liberties and preserving Obama’s policy legacy, and in opposition to a president who was moving against all those things. These were last year’s arguments, only louder. If Trump, as president, seemed unable to let go of his 2016 campaign, the Democrats seemed like they were acting out an improved version of their own — the crowds bigger and more unified, the stakes more clearly understood.