When President Trump sought to overturn his loss in the 2020 election and remain in power, resistance from within his own government helped to stop him.

Top Justice Department officials rejected his specious claims that the vote had been marred by widespread fraud. Senior officials at the Department of Homeland Security refused to go along with his outlandish efforts to seize voting machines. Cybersecurity experts praised the count as secure, and the intelligence community sidestepped his requests to declare that foreign nations had interfered in the results.

But Mr. Trump’s second term looks very different. The president has filled his administration with people who are sympathetic to his baseless claims that the presidential race more than five years ago was stolen.

These officials have been put into positions across the federal government, at the White House and in agencies where they could play a role in undermining the midterm elections and the 2028 presidential cycle.

At the same time, Mr. Trump has maintained allies in Congress and in state governments who could wield significant power over the process of counting votes and the seating of members of the House.

Abigail Jackson, a White House spokeswoman, sidestepped questions about Mr. Trump’s personnel decisions and instead asserted that he was “committed to ensuring that Americans have full confidence in the administration of elections.” She pointed to the president’s efforts to have Congress pass legislation that would require proof of citizenship to register to vote and photo identification to vote, prohibit mail-in ballots and bar the practice of ballot harvesting — having one person turn in mail ballots for several others.

“The vast majority of Americans support President Trump’s common-sense election integrity agenda,” Ms. Jackson said.

Officials from the Department of Homeland Security and the Office of the Director of National Intelligence said that the agencies were focused on keeping elections safe and secure, and were working to carry out the president’s policies on elections. The Justice Department did not respond to a request for comment.

With Mr. Trump consistently seeking to sow doubts about the integrity of elections, the number of election deniers he has installed across the administration means he would face fewer checks on any efforts to undermine an outcome he did not like, and could more easily amplify baseless claims of fraud.

Here is a look at some of the key players.

The White House has no formal or legal role to play in administering elections, but Mr. Trump recently created a presidentially appointed position to oversee election integrity and security.

That job has largely been involved in investigating the 2020 election.

Mr. Olsen was central to opening a recent F.B.I. investigation that led to the search of a Fulton County, Ga., election office in January.

Prior support for claims of election fraud

Mr. Olsen was a pro-Trump lawyer who in late 2020 contacted senior Justice Department officials on Mr. Trump’s behalf, pushing them to file a motion to nullify the election with the Supreme Court.

After 2020, he worked with Mike Lindell, the chief executive of MyPillow and a longtime election denier, to bring many unsuccessful lawsuits challenging the results of other elections and the use of voting machines, based on debunked conspiracy theories. While representing Kari Lake, a former candidate for governor in Arizona, he was hit with sanctions for making false and misleading claims.

Ms. Lake, who tried to reverse her defeat in the 2022 race, has served as the effective head of the U.S. Agency for Global Media. A judge ruled Ms. Lake’s appointment invalid, but the administration says she still works for the organization.

Mr. Parikh is working closely with Mr. Olsen to re-examine claims of fraud in the 2020 election, and was cited as a supposed expert in the F.B.I. affidavit supporting the search of Fulton County’s elections office.

Prior support for claims of election fraud

Mr. Parikh took part in Ms. Lake’s failed efforts to reverse her defeat in the 2022 Arizona governor’s race, and has served as a witness in other cases brought by Mr. Olsen challenging the use of voting machines.

In his first term, Mr. Trump issued an executive order that gave the Office of the Director of National Intelligence the ability to make determinations about foreign interference in elections. Such declarations could allow the president to declare national emergencies surrounding elections.

Ms. Gabbard is helping oversee the Trump administration’s effort to investigate supposed voting irregularities in Georgia, and was present at the F.B.I. search of the Fulton County elections office. Her office also recently seized voting machines in Puerto Rico, to examine them for vulnerability to hacking by foreign entities.

Prior support for claims of election fraud

Unlike others Mr. Trump has installed in government, Ms. Gabbard did not have a history of supporting Mr. Trump’s claims of election fraud. She started to back such claims publicly as the director of national intelligence.

The Justice Department has the power to open investigations into allegations of fraud in elections, a move that could, if nothing else, undermine faith in the results of the upcoming midterms.

Last spring, the Justice Department began seeking detailed voter roll data from states, to compile a national voting database. Under Ms. Bondi, it has sued at least 29 states and territories in an attempt to force them to turn over data.

Prior support for claims of election fraud

As a private lawyer, Ms. Bondi helped the Trump campaign seek to overturn the results of the 2020 election in Pennsylvania. She appeared at a news conference with the Trump ally Rudolph W. Giuliani, and falsely claimed that Mr. Trump had won Pennsylvania, even though not all of the ballots had been counted.

Ms. Bondi later served as the litigation chairwoman for the Trump-allied America First Policy Institute, which brought a series of lawsuits seeking to hinder ballot box access or disenfranchise groups of voters.

Mr. Patel is overseeing a criminal investigation into supposed irregularities in the 2020 presidential election that has so far led to the seizure of voting records at the Fulton County election center in Georgia, and the subpoenaing of records in Maricopa County, Ariz.

Prior support for claims of election fraud

During his Senate confirmation hearing last year, Mr. Patel sidestepped questions about whether Mr. Trump had lost the 2020 election, responding only that Joseph R. Biden Jr. had been certified and sworn in as president.

Last summer, Mr. Patel promoted an unsubstantiated theory on his social media account that thousands of fake driver’s licenses seized by customs officials in 2020 were part of a Chinese plot to throw the election that year to Mr. Biden.

Ms. Dhillon has led the Justice Department effort to obtain complete, unredacted voter roll lists from every state in the country, including suing more than half the states in an attempt to force them to turn over the data.

Prior support for claims of election fraud

Ms. Dhillon advocated efforts to overturn Mr. Trump’s loss in the 2020 election, and encouraged people to donate to his legal defense fund. Shortly after the election, she appeared on Fox Business urging Mr. Trump’s appointees on the Supreme Court to “step in and do something” to help him win the race.

She also served as a campaign lawyer for Ms. Lake and assisted her efforts to overturn her 2022 Arizona governor’s race loss.

Mr. Neff leads the voting section at the Justice Department, which is supposed to enforce the civil provisions of the federal laws that protect the right to vote.

Prior support for claims of election fraud

As a Los Angeles County prosecutor, Mr. Neff was placed on administrative leave in 2022 after basing a prosecution of the chief executive of the election management company Konnech on tips from a right-wing group, True the Vote, which has promoted conspiracy theories centered on election fraud.

Mr. Neff also served at one point as a lawyer for Patrick Byrne, the former Overstock chief executive, who advised the Trump administration to seize voting machines during the 2020 election.

Mr. Gardner is taking part in a Justice Department effort to secure voting records from Georgia officials.

Prior support for claims of election fraud

As a private lawyer, Mr. Gardner helped file a lawsuit seeking to prevent officials in Georgia from certifying the state’s 2020 election results. He also worked with other Trump-allied lawyers, including Kenneth Chesebro, John Eastman and Cleta Mitchell, to provide legal advice to a fake slate of electors in Georgia. Those electors claimed that Mr. Trump won the state even though Mr. Biden actually prevailed.

Ms. Frederick participated in a Justice Department effort demanding voter rolls from officials in the District of Columbia.

Prior support for claims of election fraud

Ms. Frederick served as a lawyer representing the Trump campaign during the Dane County, Wis., recount in 2020, and took part in efforts to challenge more than 200,000 ballots in the state.

She also worked as a leader of the Only Citizens Vote Coalition, which is part of the election-denying Election Integrity Network, an umbrella organization run by Ms. Mitchell, a stalwart pro-Trump lawyer who tried to overturn his election loss.

Mr. Voiland is active in the Justice Department’s efforts to gain access to Wisconsin’s voter registration list.

Prior support for claims of election fraud

Mr. Voiland, a former Wisconsin county judge, served as a lawyer for Mr. Trump’s 2020 campaign, and sought to have thousands of ballots in the state thrown out.

Last July, Ms. Chattah pushed the F.B.I. to investigate claims that illegal immigrants in her state had cast ballots in the 2020 election, according to Reuters. After a federal judge ruled that she had been unlawfully appointed as interim U.S. attorney, the Justice Department put her in the role of first assistant and gave her a second title as special attorney.

Prior support for claims of election fraud

Ms. Chattah joined the Republican National Committee in 2023 to advocate taking a more hard-line stance on elections, and to oust its chairwoman, Ronna McDaniel, who was seen by Trump loyalists as not doing enough to help Mr. Trump overturn the election results in 2020.

Ms. Chattah was a defense lawyer for one of the people who served as a so-called fake elector in Nevada in 2020. She also sued unsuccessfully to stop a bill that made it illegal in Nevada to harass election officials.

Ms. Pirro oversees a key federal prosecutor’s office that handles many matters related to the administration of the government.

Prior support for claims of election fraud

After Mr. Trump’s loss in the 2020 election, Ms. Pirro, then a Fox News host, used her show to amplify false allegations that voting machines made by Dominion Voting Systems had been used to rig the tally. Fox ultimately paid nearly $780 million to settle claims by Dominion that the network had defamed it through its coverage.

The Department of Homeland Security oversees multiple departments that have critical roles in election security, such as the Cybersecurity and Infrastructure Security Agency.

It has also been leading a review of election records, looking for proof of noncitizen voting. (It has not found much.)

The Senate confirmed Mr. Mullin on March 23. During his confirmation hearing, he suggested that he supported the federal investigations into the 2020 election.

Prior support for claims of election fraud

After the 2020 election, Mr. Mullin was one of the more prolific voices in Congress calling for further investigations into vote tallies. He signed a letter to Mr. Trump asking him to direct the attorney general to appoint a special counsel to investigate the 2020 election.

Ms. Honey has asserted that the Trump administration could declare a “national emergency” to justify dictating new election rules to state and local governments.

Prior support for claims of election fraud

Ms. Honey repeatedly made claims of voting irregularities in Pennsylvania during the 2020 election, and was centrally involved in the recount of Arizona’s vote tally. She also served as a witness for Ms. Lake’s failed 2022 election challenge in Arizona in a case in which Mr. Olsen worked as a lawyer. She was a leader in Ms. Mitchell’s Election Integrity Network.

The agency works to help secure election systems and assets like voting machines.

Prior support for claims of election fraud

Ms. McCarthy also worked closely with Ms. Mitchell’s Election Integrity Network and helped place far-right activists on the local election board in DeKalb County, Ga. She was instrumental in forcing out a member of the Georgia State Election Board who voted against a rule to end mail voting.

While the Federal Emergency Management Agency plays no formal role in assisting elections, its Homeland Security Grant Program has been used for cybersecurity and other election protections in the past, including in 2020, according to the Brennan Center for Justice.

Prior support for claims of election fraud

After the 2016 election, Mr. Phillips claimed without evidence that millions of illegal immigrants had cast votes — an assertion later amplified by Mr. Trump. Leading up to the 2020 election, he worked with the right-wing group True the Vote to attack mail voting as fraudulent.

He also served as the executive producer on the movie “2000 Mules,” a documentary by the conservative commentator Dinesh D’Souza that falsely claimed that a network of “mules” had illegally gathered large numbers of ballots to swing the 2020 election away from Mr. Trump.

Mr. Harvilicz oversees policies for maintaining the security of the country’s election infrastructure, including voting machines.

Prior support for claims of election fraud

Mr. Harvilicz has done business with James Penrose, a former intelligence officer who took part in several efforts to seize voting machines after the 2020 election in an attempt to undermine Mr. Trump’s defeat in the race, according to ProPublica. He has also called for doing away with voting machines, and has questioned victories of Democratic candidates.