Lori Clarke, 62, a retired schoolteacher from Bucks County, Pa., said the 2018 women’s march in Philadelphia was the first time she had attended a public protest.

“I’m just a normal everyday average woman,” Ms. Clark said. “I would never have thought of coming out to protest.”

“I hate crowds,” she added. “The reality of a Trump administration hit home, and I felt that I needed my voice to be heard.”

And in Washington, Hilary Ruesch, a 38-year-old marketing director for a wine importer, said she and others had traveled from Brooklyn to “come back to where it all began.”

They were members of a local chapter for the liberal grass-roots group Indivisible. The chapter has a mailing list of about 300 members, but in two years, the core of the group — the ones who could be counted on to do the grunt work of local political advocacy — had dwindled to about 50 people. “We’ve seen some attrition,” she said. But those who remain “are really dug in.”

And she said they played a small — but satisfying — role in the 2018 election that gave Democrats a working majority in the New York State Legislature, and in the subsequent lobbying campaign that ended this week with the Legislature’s vote to liberalize the state’s restrictive election laws.

“This time there are not as many,” Ms. Ruesch said of the march this year. “But it’s a long battle. And we still have all these people.”