Holly Cobb Robinson waits Feb. 9 to have an audience with Rep. Jason Chaffetz in Cottonwood Heights, Utah. (Kim Raff/For The Washington Post)

— The room was full of strangers, but they had a common purpose. The retired pastors who cut their teeth on the civil rights movement. The sociology professor from a local college. The grandmother of three who showed up despite having recently suffered a stroke.

“We know the Democratic majority can win if we get people to the polls,” said a woman standing in front.

“There’s a great number of Republicans who are sick to their stomachs as well,” said a 65-year-old retired consultant. “Don’t discount them.”

“Frankly, there are a lot of people, Democrats, who are not paying attention,” lamented a man next to him.

Kimberly Anne Tucker sat and listened. A few months ago, she was like them, with a sinking feeling about a country that had elected Donald Trump to the presidency and an urge to do something about it. One night after Trump’s inauguration, after watching “The Rachel Maddow Show,” she opened her laptop and signed on to lead Indivisible 757, the southeastern-Virginia branch of a new national group opposed to Trump.

(Taylor Turner/The Washington Post)

Within weeks, the group swelled to 2,500 members. They started staging protests at the Virginia Beach Town Center and had a candlelight vigil for the Affordable Care Act outside their Republican congressman’s office. A sister organization, HOPE, popped up to support local refugees and immigrants. Several smaller breakout groups followed, including this one, which brought 20 people out on a rainy Sunday afternoon to plot ways to push this coastal Virginia region to be more blue.

The work has given Tucker, 50, a retired teacher and school administrator who a few months ago was focused on raising her 18-month-old granddaughter, a way to channel her concerns.

“Of course, part of our agenda is increasing voter engagement,” she said. “But we just never, ever, will turn away from our primary responsibility of resistance to Trump.”

One hundred days after Trump took office, the resistance efforts that grabbed headlines in the form of massive women-led marches across the country the day after the inauguration have settled into something less visible but perhaps much broader.

The resistance has been mounted on a number of fronts, by venerable organizations such as the American Civil Liberties Union and Planned Parenthood, as well as upstarts such as the Indivisible Project and the Women’s March. Many U.S. cities have pledged to remain “sanctuaries” for people living in the country illegally despite President Trump’s threat to withhold federal grants from those cities, and states such as Hawaii and Maryland have filed lawsuits over his executive order seeking to ban travelers from some Muslim-majority countries.

The foot soldiers are the men and women who have joined thousands of groups such as Indivisible 757 that have formed nationwide, from Virginia Beach to Orange County, Calif.

It is unclear whether this nascent Democratic movement can maintain enough momentum to create change as effectively as tea party conservatives did after Barack Obama’s election. That movement, which grew out of conservative outrage, pushed the GOP to the right and laid the groundwork for Trump’s victory.

Liberals seeking to build a similar power base face different challenges. They remain fractured after the election, some still identifying as supporters of Hillary Clinton or her foe in the Democratic primary, Sen. Bernie Sanders (I-Vt.). They argue over ideological purity, such as whether there is space in the Democratic Party for opponents of abortion rights, for example.

Progressives have other structural challenges that make their task more difficult, particularly their concentration in big cities and university towns and their tendency to mobilize more for presidential elections than state and local ones.

But these newly energized activists say they are well aware of the hurdles. They hope to avoid them by remaining engaged beyond the presidential level and becoming well versed in the minutiae of the democratic and political processes.

“We’re not in a position anymore where people of mild intelligence and reasonable interest in the political system . . . can just read the newspaper and vote and be done, figuring the people in charge will just take care of things,” said Elizabeth Juviler, a commercial real estate broker and head of a resistance group in the New Jersey suburbs of New York. “There is no one in power who can take care of it any better than any of our friends or neighbors could do it.”

So they send handwritten postcards to members of Congress, or cram into town hall meetings, or inundate them with phone calls to urge legislative action. Constituent pressure such as this led two Republican senators to abandon support for Trump’s education secretary nominee, who was confirmed only when Vice President Pence broke a Senate deadlock. It is also credited with leading a number of moderate Republicans to abandon support for the GOP replacement for the health-care law.

The Indivisible Project recently urged supporters to learn how to submit comments on proposed federal rules to roll back the Clean Air and Clean Water acts, an action meant to show a force of opposition as well as throw sand in the Environmental Protection Agency’s gears.

“At one extreme you have mass protest. At the other extreme you have very targeted electoral work,” said Beverly Gage, a Yale University history professor. “In between there is a huge political toolbox in this country, and probably if the movements are going to be effective, they are going to use all the tools and see which ones really work.”

One advantage for liberals is that an outsize proportion of the Democratic Party is made up of women, and women are particularly adept at local organizing, said Theda Skocpol, a Harvard University political-science professor who has studied the tea party movement, which gained a significant push from women.

“They were baking the goods for the fundraising table. They were providing the local leadership. That’s what it’s always been like in civic engagement,” Skocpol said. “On the Democratic side, you’re going to see that even more because Democrats are disproportionately women.”

For Tucker’s group, the goal is concrete, because Virginia — a purple state that narrowly backed Clinton in the presidential election — is one of only two states holding a full slate of elections this year. So on Sunday, a Virginia Beach contingent of Indivisible 757, named for the local area code, gathered in a member’s living room to plot how a Democrat might be able to beat Del. Jason S. Miyares (R) in November’s state legislative election.

It will be an uphill battle. Trump won this Republican-leaning House of Delegates district with 55 percent of the vote; it has been in Republican hands since at least the 1980s. But the group was heartened about prospects in Congress after strong showings by Democrats in recent special elections in the deep-red states of Georgia and Kansas. Group members were optimistic that they could make headway by coaxing some of their Republican neighbors to their side and mounting a robust get-out-the-vote campaign.

But the challenges were on display, too. Some lamented that there aren’t more young people in the group, which leans heavily in the direction of retirees who are already active in Democratic organizations. Others grumbled that the Democratic Party’s failings paved the way for Trump’s victory.

And it didn’t take long for the Sanders-Clinton feuding to begin. Mike Callahan, 65, a retired consultant and a Sanders supporter, railed about Bill and Hillary Clinton’s Wall Street ties and what he saw as the Democratic establishment’s abandonment of working people.

“I get it. It’s all about the money for some people,” Susan Rooney, 59, a real estate agent, shot back. “No rights matter unless women’s rights are included. . . . Bernie Sanders, he’s not real strong on women’s issues.”

Tucker tried to get the neighbors to focus on their common ground. “It’s about unity,” she told them.

Someone asked whether it made sense to schedule a follow-up meeting in May.

“Yes!” Rooney said. “We were just getting something started here.”