Last fall, Hannah Dasgupta spent her days focused on politics, channeling her fear and anger over President Donald J. Trump into activism. Worried about the future of abortion rights, among other issues, during the Trump administration, she joined a group of suburban Ohio women who were working to elect Democrats.

A year later, Ms. Dasgupta, 37, still cares just as deeply about those issues. But she’s not planning on attending a nationwide women’s march for abortion rights on Saturday. In fact, she hadn’t even heard about it.

“I don’t watch the news every single night anymore. I’m just not nearly as concerned,” said Ms. Dasgupta, a personal trainer and school aide, who was devoting her attention to local issues like her school board. “When Biden finally got sworn in, I was like, ‘I’m out for a little while.’”

Ms. Dasgupta’s inattention underscores one of the biggest challenges facing the Democratic Party as it looks to the midterm elections. At a moment when abortion rights face their most significant challenge in nearly half a century, a portion of the Democratic grass roots wants to take, in Ms. Dasgupta’s words, “a long breather.”

The march on Saturday, sponsored by a coalition of nearly 200 civil rights, abortion rights and liberal organizations, offers an early test of Democratic enthusiasm in the post-Trump era, particularly for the legions of newly politically engaged women who helped the party win control of Congress and the White House.

In 2017, the first Women’s March drew an estimated four million protesters into streets across the country to voice their outrage at the inauguration of Mr. Trump. Many listed abortion rights as a motivating issue, according to surveys of participants. Since then, the annual events have drawn smaller crowds, and the organizers have found themselves dogged by controversies and internal strife.

Organizers of the abortion rights march on Saturday are trying to lower expectations, describing the event as the start of their efforts to combat restrictions and citing public health concerns as a reason for an anticipated low turnout. They expect about 40,000 attendees at hundreds of events in cities around the country — a mere fraction of the millions who protested during the Trump administration.

Those who are not attending say the reasons are varied: The coronavirus pandemic; a sense of political fatigue after a divisive election; other issues that seem more pressing than abortion, such as racial justice or transgender rights.

“There would have been a time when a march like this would have been a three-generational event,” said Celinda Lake, a Democratic pollster who advises the White House and the Democratic Party. “Now, the 8-year-old girl isn’t vaccinated and you’re scared that Mom could get sick. People are just exhausted and they’re deliberately checking out.”

Even as Democrats see the struggle over abortion rights as a winning political fight, party strategists worry that a decline in enthusiasm could be another harbinger of what’s expected to be a difficult midterm election next year for their party.

Already, Democrats find themselves struggling to respond to a series of public health, economic and foreign policy crises. As party factions bicker and Mr. Biden’s approval ratings sink, his domestic agenda remains mired in a legislative standoff in Congress. Other issues that would motivate the Democratic base, including legislation that could enact abortion rights into federal law, face an uphill climb to passage given the party’s razor-thin congressional margins.

In interviews and polling, voters who believe abortion should remain legal say they worry about the future of abortion rights and say restrictions, such as a new law in Texas banning abortions after about six weeks, make them more likely to vote in the midterm elections.

But they are also skeptical that the constitutional right to an abortion will be completely overturned and view managing the pandemic as far more urgent. And some of those who became activists during the Trump administration now prefer to focus on state and local politics, where they see more opportunities to enact change. Other solutions to protect abortion rights proposed by liberal groups — including expanding the Supreme Court — remain divisive among independent voters.

Abortion rights advocates warn that this is no time for complacency. The Supreme Court is preparing to take up an abortion case — the first to be argued before the court with all three of Mr. Trump’s conservative appointees — that has the potential to remove federal protection for abortion altogether.

“We have almost 50 years of legal abortion,” said Amy Hagstrom Miller, the chief executive at Whole Woman’s Health, which operates four clinics in Texas. “People don’t believe it could roll back.”

Some advocates believe voters will become more engaged as similar bills to the Texas law pass other Republican-controlled state legislatures. Aimee Arrambide, the executive director of Avow Texas, an abortion rights organization in Austin, struggled to generate attention when the Texas law was first introduced. Since the bill became law last month, her organization has collected $120,000 in donations, an amount that would normally take six months to raise.

“It’s a little frustrating because we’ve been kind of sounding the alarm for years, and nobody was really paying attention,” she said. “People are realizing that the threat is real.”

For decades, opponents of abortion rights have attracted large crowds to the National Mall in Washington for the March for Life, an event that often draws thousands of activists and features high-profile conservative politicians and religious leaders. On Monday, thousands gathered outside the Pennsylvania State Capitol in Harrisburg urging the passage of anti-abortion legislation.

The liberal movement that exploded into the streets in 2017 was led and fueled by women, many of them college-educated and often middle-aged. They gathered for huge marches and almost weekly protests, huddling to discuss door-knocking strategies in exurban Paneras and founding new Democratic groups in tiny, historically conservative towns. Many of the marchers came to these events with their own parcel of pressing issues, but surveys showed the issue that the persistent protesters most had in common was abortion rights, said Dana R. Fisher, a sociology professor at the University of Maryland who has conducted surveys among activist groups and at large marches.

Those motivations began to change in the last two years. As the threat of Covid-19 kept many of the older activists home, the killing of George Floyd at the hands of the police in May 2020 ignited an even larger wave of demonstrations nationwide, which were fueled by younger crowds motivated by a different set of issues.

In surveys conducted at marches following the killing of Mr. Floyd, as well as among organizers of last year’s Earth Day demonstration, the percentages of people citing abortion rights as a key motivator for activism were much lower, Ms. Fisher said.

And while Mr. Trump may have been defeated, the issues that his presidential tenure highlighted for many activists have not gone away.

“There’s a sense that people are just hopeless,” said Judy Hines, who is a retired gym teacher in a conservative rural county in western Pennsylvania and who is active in Democratic politics.

Ms. Hines welcomed the jolt of new energy that followed the 2016 election: Local meetings were packed, political rookies ran for office and hundreds attended marches in the county seat. Later, as the energy started to slowly dissipate, the coronavirus shut it off “like a switch,” she said. Ms. Hines has not been to a march in more than a year and a half, and since she has a family member with health issues, she is not planning to attend on Saturday either.

“I’m hoping that the fight is still in people but it’s not,” she said. “We see our Supreme Court. We know how they’re going to vote.”

David Montgomery contributed reporting from Austin.