ELIZABETHTOWN, Pa. — When thousands of Trump supporters gathered in Washington on Jan. 6 for the Stop the Steal rally that led to the storming of the U.S. Capitol, one of them was a pastor and substitute teacher from Elizabethtown, Pa., named Stephen Lindemuth.

Mr. Lindemuth had traveled with a religious group from Elizabethtown to join in protesting the certification of Joseph R. Biden’s victory. In a Facebook post three days later, he complained that “Media coverage has focused solely on the negative aspect of the day’s events,” and said he had been in Washington simply “standing for the truth to be heard.”

Shortly after, he declared his candidacy for judge of elections, a local Pennsylvania office that administers polling on Election Day, in the local jurisdiction of Mount Joy Township.

Mr. Lindemuth’s victory in November in this conservative rural community is a milestone of sorts in American politics: the arrival of the first class of political activists who, galvanized by Donald J. Trump’s false claim of a stolen election in 2020, have begun seeking offices supervising the election systems that they believe robbed Mr. Trump of a second term. According to a May Reuters/Ipsos poll, more than 60 percent of Republicans now believe the 2020 election was stolen.

This belief has informed a wave of mobilization at both grass-roots and elite levels in the party with an eye to future elections. In races for state and county-level offices with direct oversight of elections, Republican candidates coming out of the Stop the Steal movement are running competitive campaigns, in which they enjoy a first-mover advantage in electoral contests that few partisans from either party thought much about before last November.

And legislation that state lawmakers have passed or tried to pass this year in a number of states would assert more control over election systems and results by partisan offices that Republicans already decisively control.

“This is a five-alarm fire,” said Jocelyn Benson, the Democratic secretary of state in Michigan, who presided over her state’s Trump-contested election in 2020 and may face a Trump-backed challenger next year. “If people in general, leaders and citizens, aren’t taking this as the most important issue of our time and acting accordingly, then we may not be able to ensure democracy prevails again in ’24.”

In some areas, new political battlefields are opening up where none existed before.

Until this year, races for administrative positions like judge of elections were noncompetitive to the point of being more or less volunteer opportunities. Candidates ran unopposed, or sometimes not at all: The seat that Mr. Lindemuth ran for had been technically unoccupied before his election, filled by appointment by the County Board of Elections.

“There’s a lot of apathy here,” said Lisa Sargen Heilner, a former Republican committeewoman in Mount Joy Township, who resigned her post shortly after local Republicans endorsed Mr. Lindemuth and his wife, Danielle, in a concurrent school board election in which they both won seats. “I just kind of wanted to disassociate myself from them,” Mrs. Heilner said.

After Mr. Lindemuth won the G.O.P. primary for judge of elections in the spring, local Democrats struggled to find a candidate until Mike Corradino, an academic dean at a local community college, volunteered. “Like a lot of people, it troubles me what happened on Jan. 6,” Mr. Corradino said. He lost with 268 votes to Mr. Lindemuth’s 415.

Kristy Moore, the local Democratic committeewoman and a seventh-grade English teacher who ran unsuccessfully against Mr. Lindemuth in the school board race, said she had tried to attract the attention of county and state Democrats, but to no avail.

“I’m not sure what the Democratic Party was worried about, but it didn’t feel like they were worried about school board and judge of elections races — all of these little positions,” she said.

Mr. Lindemuth, whose phone was answered by a woman who refused to identify herself but declined to comment on his behalf, told The Atlantic in November that he saw the job as a public service. “It really has little to do with election results,” he said. “It’s more about filling in the gaps for the community.”

But Mrs. Heilner said that Mr. Lindemuth was unknown in local Republican circles before he announced his candidacy, and Mr. Corradino expressed concern about his Jan. 6 involvement. “I hope that once he sees the responsibilities and the training, that would be a moderating influence,” Mr. Corradino said.

“I’m hoping that we don’t have any constitutional crises in our neck of the woods,” he added. “But things are a bit scary.”

In the months immediately after the election, Mr. Trump’s campaign to discredit the election’s outcome fueled a wave of lawsuits and partisan audits in closely contested states, none of which turned up evidence of more than extremely isolated instances of fraud.

This activity — fueled by grass-roots activists, party donors, sitting Republican politicians and Mr. Trump himself — has evolved rapidly into an effort that looks forward, not backward: recruiting like-minded candidates for public offices large and small, and proposing and, in some cases, passing laws intended to give partisan actors more direct control over election systems.

At every level, opponents are operating at a steep disadvantage. The electoral battles are being fought largely in areas where Democrats have struggled to maintain a foothold for over a decade. The legislative pushes are occurring in states where Republicans dominate both legislative and executive offices, and federal responses have been blocked by unified Republican opposition and Senate rules, which a dwindling but decisive number of Senate Democrats have resisted changing.

Throughout, there is a stark asymmetry of enthusiasm: Where Mr. Trump’s partisans see the issue of election system control as a matter of life and death, polling suggests Democratic voters broadly do not.

Secretaries of state like Ms. Benson, charged with administering elections in their states, are among the most visible targets of the Stop the Steal movement, and the clearest examples of how Mr. Trump’s election claims have opened up new, lopsided political terrain in heretofore sleepy corners of the electoral system.

Although they run on party tickets, secretary of states’ campaigns have generally been amicable contests among bureaucratic professionals who pride themselves on placing civic responsibility over their parties’ pursuit of power. All of that changed when Mr. Trump and his allies, fuming over his loss in 2020, portrayed a handful of swing-state secretaries of state as supervillains, often wielding false claims of election malfeasance against them.

After Brad Raffensperger, Georgia’s Republican secretary of state, resisted Mr. Trump’s personal pressure to overturn the election results, Mr. Trump denounced him at rallies and Mr. Raffensperger and his family became the targets of regular death threats. Demonstrators, some of them armed, gathered outside Ms. Benson’s home last December shortly after Mr. Trump baselessly claimed that there had been “massive voter fraud” in Michigan’s election.

A year later, Trump loyalists supporting his claims about the 2020 election are strong candidates and, in some cases, front-runners in Republican primaries for secretary of state across the country. In Georgia, Representative Jody Hice, who has said he is not “convinced at all, not for one second, that Joe Biden won the State of Georgia,” is running against Mr. Raffensperger in the Republican primary in May, with Mr. Trump’s backing.

In November, Ms. Benson may find herself running against Kristina Karamo, a community college adjunct professor who has claimed that the 2020 elections were fraudulent, advocated for removing “traitors” from the Republican Party and accused Democrats of pursuing a “satanic agenda.” Since Mr. Trump endorsed her in September, she has considerably out-raised her rivals for the Republican nomination. (Ms. Karamo’s campaign did not respond to a request for comment.)

Democrats fear that such contests may pit a highly motivated Republican base that has come to view these races as central fronts in the battle for America against Democratic voters who are barely aware the races are happening at all.

“They have Trump hitting this one note all the time,” said Pete Brodnitz, a Democratic pollster. Among Democrats, he said, “If you ask people what their concerns are, about Republicans or their daily lives, they don’t say ‘threats to democracy.’”

In a PBS News Hour/NPR/Marist Poll in October, 82 percent of Democrats said they would trust the results of the 2024 presidential election to be accurate if their candidate did not win; only 33 percent of Republicans did. Other questions about the integrity and fairness of the election system consistently yielded comparable divides between the parties’ voters.

Traditional campaign organizations have been slow to involve themselves significantly in secretary of state races, much less local election oversight offices.

“Donald Trump and a lot of folks in his orbit were frankly ahead of the curve when it came to raising funds and organizing behind candidates who backed the big lie,” said Miles Taylor, a former official in Mr. Trump’s Department of Homeland Security who this year helped to start the Renew America Movement, an organization supporting Republican and Democratic candidates running against Trump-backed Republicans.

Mr. Taylor said that while his group was now active in congressional races, it did not yet have the resources to compete against Trump-endorsed candidates in state contests. Nor was the Democratic Party capable of filling the void, he said: “In a lot of these places, Democrats have no hope of winning a statewide election, and all that matters is the primary.”

In other areas, Democrats are disadvantaged by pre-existing political losses. In 23 states, Republicans control both state legislatures and governors’ mansions. Democrats control both in only 15 states.

The legislatures that Republicans now control have in the past year become laboratories for legislation that would remove barriers that stood in the way of Mr. Trump’s efforts to overturn the 2020 results. In seven states this year, lawmakers proposed bills that would have given partisan officials the ability to change election results in various ways. Although none passed, Republican-led legislatures in Arizona and in Georgia passed laws that directly removed various election oversight responsibilities from the secretaries of state — legislation that appeared to directly target specific officials who had been vilified by Mr. Trump.

“We’ve never seen anything like that before,” said Wendy Weiser, the vice president for democracy at the Brennan Center for Justice at New York University School of Law, who co-wrote a recent report on the new state-level legislation.

Ms. Weiser and other advocates have called for federal legislation to head off such efforts. “We must have that in order to have a comprehensive response,” said Norm Eisen, co-chair of the States United Democracy Center. But with the Democrats most likely to lose one or both houses of Congress in the next two election cycles, the time to pass it is fleeting.

Several election and voting rights reform bills have foundered this year upon unified Republican opposition in a Senate where Democrats hold a one-vote majority. Ten Senate Republicans would need to break ranks in order to overcome the party’s filibuster of the legislation. Only one, Lisa Murkowski of Alaska, has voted for any of the bills so far.

Among the very few prominent Republicans who have supported federal efforts to curb the state legislatures’ power grabs, some have faulted congressional Democrats for spending the early months of the year trying to pass a sweeping voting reform bill that included longstanding policy priorities like campaign-finance reform that were anathema to Republicans and not directly related to heading off the threats to election systems.

“That wasn’t something that was going to pass, and everybody knew it,” said Sarah Longwell, a Republican strategist and the executive director of the Republican Accountability Project.

But Ms. Longwell also acknowledged that any Democrat-sponsored voting rights bill was dead on arrival in the Senate. “I think they would’ve run into the same problems,” she said. “After the election, Republicans were locked in.” This year, her organization started Republicans for Voting Rights, a campaign endorsing a compromise bill co-sponsored by Joe Manchin III, the West Virginia Democrat, and trying to rally Republican support for it. The legislation earned zero Republican votes.

“I just don’t see it,” said Amy Klobuchar, the Minnesota Democratic senator, who has sponsored bipartisan voting bills in the past and led bipartisan Rules Committee hearings on election threats this year. “We have tried every which way — not just Senator Manchin. A number of us tried and talked to them repeatedly for months.”

Ms. Klobuchar is among an increasing number of Senate Democrats, including many of the party’s moderates, who have called for the filibuster rule’s elimination or reform this year — as has Mr. Biden, who said that he was “open to fundamentally altering the filibuster” at a CNN town hall in October.

Several of the moderates have been meeting regularly with Mr. Manchin, the caucus’s most determined holdout, in recent months to discuss potential changes.

The Hill newspaper reported this week that Mr. Manchin was in talks with some Senate Republicans about small changes to the rule that might prove acceptable to both parties, but the changes reportedly discussed appear unlikely to make passage of the proposed election and voting reform legislation any more likely.

“I am frustrated that at this point, after everything we endured last year and after we all witnessed what happened on Jan. 6, there isn’t more of a sense of urgency,” Ms. Benson said. “We all have to band together and say, ‘Never again’ — as opposed to saying, ‘Well, maybe it will happen again, and maybe we’ll be ready.’”