This could be the Scott Brown moment for the young movement that has risen up to oppose the agenda of Mr. Trump and the Republican-led Congress, providing the taste of power that Tea Party groups got in 2010 when they helped elect Mr. Brown, a Massachusetts Republican, to a Senate seat that had been held for decades by a Democrat. That victory propelled a wave of conservative victories in the midterm elections later that year.
But for liberal groups, the swift success in health care removes a visceral, unifying issue. And with the midterms much farther off than they were after Mr. Brown’s victory in a special election — 20 months away, not 10 — many resistance-group leaders worry about sustaining their momentum into 2018.
“The nightmare scenario is two years from now it’s, ‘Hey, remember when we all did activism?’” said Ezra Levin, a co-founder of Indivisible, a group that wrote a guide to resisting the Trump agenda and is helping to nurture resistance groups.
“There is always a fear that there’s a ton of energy now, but these are not professional organizers. They are doing this in their free time — nights, weekends, sick days,” he said. “This is tough work to do.”
While the Tea Party united largely around one goal for seven years — abolishing the health law it derisively called Obamacare — members of the new resistance have a host of next priorities: pushing an investigation of ties between Russia and the Trump campaign, getting Mr. Trump to release his tax returns, and reversing his executive orders to restrict immigration and loosen environmental protections.
“People care about these issues, but it’s not as direct as ‘I’m not sure I’ll be able to go to my doctor,’ or ‘I’m not sure this procedure I was going to have next month I’ll still be able to have,’” said Vanessa Williamson, a co-author, with Theda Skocpol, of “The Tea Party and the Remaking of Republican Conservatism.”
“When the costs are not so immediate,” she said, “it’s hard to mobilize people.”
Many of the groups started out organizing demonstrations at town hall-style meetings during the February congressional recess. These encounters produced arresting video of angry constituents facing down their elected representatives.
But for the Easter recess, which starts this week, there is less focus on town halls.
Instead, many groups have already moved on to developing strategies for the 2018 elections. Groups like this one in New Jersey are forming political action committees and raising money. Others, just as the Tea Party groups did, are beginning to train their members on how to go door to door and use data to get out the vote. In some districts where Republicans won their seats narrowly, several Democrats are already lined up to run.
To be as effective as the Tea Party, Ms. Williamson said, resistance groups will have to focus on politics and policies within their own states as well. While the Tea Party got a lot of attention for the energy it brought to congressional elections, it was also effective on the state level, particularly as a force blocking Medicaid expansion under the Affordable Care Act.
Guy Potucek, who works for a military contractor and organized an Indivisible group in Virginia’s 10th District, represented by Barbara Comstock, said his group had held a training session to help members get involved in the Virginia elections this year.
“I don’t want them jumping all the way to 2018,” he said.
Ms. Comstock was among the Republicans who announced late in the game that she would not support the party’s health bill. “It energized us even more,” Mr. Potucek said. “It felt like, ‘That was easy.’”
But now, he said, “I’m also worried about properly pacing ourselves.”
“If we said, ‘Just make a call now and then,’ we’d lose steam that way,” he continued. “If we were asking people in the group to show up every week at Comstock’s office, I think we would also lose steam that way.”
He has been sending out “action alerts” to the 3,500 members of the group’s email list, asking them to post on social media and write and call their representatives on a different talking point each week. This week, it was pushing legislators to expand Medicaid. (On Wednesday, the state’s legislature voted against expansion.)
He is also asking members to write letters to the editors of local papers about Ms. Comstock’s voting record.
“The more we can over time show how her voting record is tied to Donald Trump, we can make it easier for the eventual Democrat running against her,” Mr. Potucek said.
As many as 10 candidates are considering running against Ms. Comstock, he said; one has declared, and shown up to meetings to seek support, and four others have reached out.
In California’s 49th District, where Representative Darrell E. Issa, a Republican, won re-election by less than 1 percent of the vote in November, leaders of a dozen resistance groups have organized a training session for early next month to write scripts that members can use when talking to neighbors about the importance of the midterms. They are creating databases of voters that the new activists can use to host pizza parties or coffees, and to track door-to-door visits as they canvass for the midterms, in which two Democrats, including the one who lost narrowly in November, have already signaled an intention to run.
One organizer, Terra Lawson-Remer, has written a 50-page campaign blueprint identifying five groups of voters to target for the midterms. They include Democrats in cities where voter turnout has been low in off-cycle elections, Orange County Republicans who did not support Mr. Trump, and members of the military at Camp Pendleton who might be concerned about Russian interference in the 2016 elections.
In New Jersey, members of NJ-11th for Change had been rallying outside the office of their congressman, the Appropriations Committee chairman, Representative Rodney Frelinghuysen, every Friday since January to ask him to meet with them — unsuccessfully. The crowd eventually grew to 450 people.
Their first rally after Republicans pulled their health care bill was smaller, drawing only about 150. But new faces turned out, including Ted Noble, a 73-year-old Vietnam veteran from Wayne, who said he was concerned about Mr. Trump’s budget.
“We got to take care of people who need help,” Mr. Noble said. He teared up as the group began to gather for the walk to Mr. Frelinghuysen’s office. “I think it’s phenomenal what you’re doing,” he told an organizer.
Last week, the group organized a bus trip to Washington. The evening before, it got another small victory: Mr. Frelinghuysen, at long last, had agreed to a meeting.