Voting rights advocates are furious at President-elect Donald Trump’s baseless claims of widespread voter fraud and concerned that his administration will more vigorously adopt measures that will make it harder for some groups of people to vote.

Some state and local election officials in recent years have cited the potential for voter fraud as the reason for enacting strict voter-ID laws, requiring additional verification for people who want to register to vote and conducting mass purges of voter rolls. Trump’s promotion of the widely debunked notion of rampant voter fraud and the presence in his inner circle of political leaders who supported stricter voting laws send a troubling signal, say advocates who have spent the past several years fighting what they say are efforts to disenfranchise minorities and young, elderly and low-income voters.

“They don’t want us to participate in this democracy,” said Cristóbal J. Alex, president of the Latino Victory Project. “We are gearing up for what will be the biggest fight of our lifetime.”

In the weeks leading up to the Nov. 8 election, Trump often claimed that the election would be “rigged” and urged his supporters to monitor polling places in “certain areas.” Trump was elected president by racking up the most electoral votes, but Democrat Hillary Clinton’s lead in the popular vote has continued to grow. That prompted the president-elect to fire off a series of tweets on Sunday pushing a baseless allegation that Clinton won the popular vote because of “millions of people who voted illegally.” He specifically cited, without providing evidence, irregularities that he said took place in California, New Hampshire and Ohio.

There's a group of people in the United States and its territories who have historically faced disenfranchisement, including felons and certain U.S. nationals. (Jenny Starrs/The Washington Post)

Referring to that most recent comment, Sen. Bernie Sanders (Vt.), who during his Democratic presidential campaign often accused Republicans of engaging in voter suppression, said, “When you’ve got this delusional, crazy tweet from the president-elect, you are sending a signal to the entire administration that their goal is to go forward and suppress the vote.”

Trump’s transition office did not respond to a request for comment on Tuesday. Trump spokesman Jason Miller declined to say at a Monday news briefing whether the president-elect’s Justice Department would ask state or federal law enforcement to investigate allegations of illegal voting but said there is “concern that so many have voted who were not legally supposed to.”

Among those concerned about the Trump administration’s approach is Chris Carson, president of the League of Women Voters, who said last week in a statement on the group’s website, “This election was rigged.” But she was referring to what she and other advocates describe as “voter suppression.”

In an interview this week, Carson cited Ohio, where, in violation of federal law, officials dropped 400,000 voters from the rolls because they had not cast ballots in recent elections. The league sued, and a federal court ordered the voters reinstated a few weeks before the election. Carson said league members scrambled to call as many voters as they could.

The league also sued to block the states of Kansas, Alabama and Georgia from requiring people to show proof of citizenship to register to vote. “We’re not going to sit here and accept . . . that we can just willy-nilly restrict the right of eligible citizens to vote,” she said.

Many of the laws that advocates have fought were put in place after the Supreme Court’s 2013 decision striking down a section of the 1965 Voting Rights Act that required states with a history of discrimination against minority voters to seek the Justice Department’s approval before making changes in voting laws and procedures. A law in North Carolina that required voters to show a specific type of ID, cut out a week of early voting and called for other restrictions was struck down by a federal court in July, which described it as “the most restrictive voting law North Carolina has seen since the era of Jim Crow.”

Kristen Clarke, president and executive director of the Lawyers’ Committee for Civil Rights Under Law, said the group’s Election Protection coalition was contacted by 117,000 voters and would-be voters who had problems during the election cycle. “We did not receive any complaints of voter fraud, but we received plenty of complaints of elections officials requiring identification where there was no such requirement in place, of polling machines malfunctioning, of individuals brandishing weapons at polling sites, of students being told they were not eligible to vote,” she said.

“To suggest that vote fraud is rampant across our country invites states to put in place laws making voting more difficult, and that is incredibly anti-democratic,” she said.

Wendy Weiser, director of the Democracy Program at the Brennan Center for Justice at the New York University School of Law, said the Trump administration could change the voting landscape in a few ways. They include not filing lawsuits against states in which voter suppression is alleged, pressing for more aggressive purges of voter rolls or trying to push legislation through Congress, Weiser said.

The president-elect’s statements and some appointments and Cabinet nominations that he has made have been of particular concern to groups that fear that a Trump administration could move to suppress voting among black, Hispanic, elderly, young and rural voters. They are worried about Trump’s nomination of Sen. Jeff Sessions (R-Ala.) to be attorney general and his appointment of Kansas Secretary of State Kris Kobach, an anti-illegal-immigration hard-liner, to his transition team. Kobach also has pushed rules — which were challenged in court — that would require proof of citizenship for those seeking to register to vote. And they fear that a Trump appointee to the Supreme Court could undermine voting rights.

Representatives for Sessions and Kobach declined to answer questions or did not respond to emails from The Washington Post.

Sessions’s nomination to the federal bench was rejected in 1986 in part because of a voting rights case he handled while U.S. attorney in Alabama. Sessions’s office alleged then that three black civil rights activists in Perry County, Ala., had tampered with absentee ballots. The activists argued that they changed the ballots with the consent of elderly and illiterate voters and that they were being targeted to suppress the black vote.

Kobach is one of the nation’s foremost advocates for adding more requirements for people to vote or register to vote. He is considered a possible candidate for a Trump Cabinet post.

“Given the troubling rhetoric and records of the president-elect and his nominee for attorney general, I am deeply concerned that the Trump administration will use totally unsubstantiated claims of voter fraud of this nature to make it more difficult for citizens to vote,” said Rep. John Conyers Jr. (D-Mich.), who participated in the 1963 voter registration drive known as Freedom Day in Selma, Ala.

But Francis De Luca, president of the Civitas Institute, has filed a federal lawsuit in North Carolina asking that ballots cast by people who used same-day registration not be counted until those people can be verified as eligible voters.

De Luca waved off Trump’s comments about voter fraud as “over the top,” but he said he does think that there is “a lot more voter fraud than is reported.” He said voter fraud on a scale sufficient to affect a presidential election is unlikely but cited a few instances in North Carolina in which local elections turned on a handful of votes.

He said he supports strict voter-ID laws and other measures that protect the electoral process. “You have to show ID to get a drink in a bar,” he said. “Underage drinking is illegal, and it’s illegal to cast a ballot in someone else’s name.”

However, even some Republicans are pushing back against Trump’s claim that the election was not conducted fairly. Thomas D. Rath, a Republican who has been active in New Hampshire politics and elections for decades and served as the state’s attorney general, vigorously rejects Trump’s contention that the results in New Hampshire were fraudulent.

“This election was as fair and honest as anywhere you will find in the country,” he said. “I don’t think it’s a partisan question. I think the idea of doing elections and getting them right is really very important.”

Nationwide, there is skepticism that the nation’s elections are fair. In September, 46 percent of registered voters said voter fraud happens very often or somewhat often, according to a Washington Post/ABCNews poll. Nearly 7 in 10 Trump supporters said voter fraud happens often, compared with 28 percent of Clinton backers.

After the election, 99 percent of Trump supporters surveyed said they accept Trump as the legitimate winner — but they had many reservations before the election. In the week before, just 69 percent of Trump supporters surveyed said they were prepared to accept the legitimacy of the results.

Scott Clement and Michelle Ye Hee Lee contributed to this report.

Correction: An earlier version of this article said 117,000 voters and would-be voters contacted the Election Protection coalition about problems on Election Day. That total provided by Kristen Clarke was for the full election cycle.