Republican presidential nominee Donald Trump threatened to jail people “involved in unscrupulous behavior” related to voting in the 2024 election, suggesting without evidence that the election could be stolen from him — and prompting widespread condemnation from election officials who said such rhetoric could provoke violence.

Trump’s remarks, made in a social media posting on Saturday night, represent the most overt signal yet that he may not accept the result in November if he loses.

Trump has a history of railing against election officials and raising unsubstantiated claims of fraud when his political fortunes appear uncertain, as they do now in his extremely close race with Vice President Kamala Harris. His comments are his most direct threats made against those tasked with administering elections this year.

In reality, illegal voting is exceedingly rare. But Trump appears to be replaying his efforts to sow doubt about the voting process ahead of the 2020 election — actions that contributed to the deadly Jan. 6, 2021, attack on the Capitol.

“WHEN I WIN, those people that CHEATED will be prosecuted to the fullest extent of the Law, which will include long term prison sentences so that this Depravity of Justice does not happen again,” Trump wrote on Saturday on his Truth Social platform. “We cannot let our Country further devolve into a Third World Nation, AND WE WON’T!”

Trump, who began his message with the words “CEASE & DESIST,” went on to threaten a wide range of the kinds of people who would face prosecution and prison time, including campaign donors and those involved in administering elections.

“Please be aware that this legal exposure extends to Lawyers, Political Operatives, Donors, Illegal Voters & Corrupt Election Officials,” he wrote, adding that such people will be “sought out, caught, and prosecuted at levels, unfortunately, never seen before in our Country.”

David Becker, who foundedthe nonprofit Center for Election Innovation & Research, urged the public to reject Trump’s inflammatory language.

“I can’t begin to describe the abnormality and disturbing behavior that would cause a presidential candidate, a former president, to threaten public servants with mass arrest,” said Becker, who previously worked as a lawyer for the Justice Department for seven years.

Several election officials also called threats of violence “unacceptable.”

“Donald Trump will not accept the results of the election unless he wins,” said Colorado Secretary of State Jena Griswold (D). “This is another step in his campaign to undermine confidence in our elections, which has led to unprecedented threats of violence against election officials.”

A spokesperson for the Trump campaign did not reply to a request on Sunday afternoonfor comment on Trump’s post.

On Sunday, Trump doubled down on his baseless claims of election fraud, saying on Truth Social that he expects to win the key swing state of Pennsylvania “by a lot, unless the Dems are allowed to CHEAT.”

Late last month, during a conversation with the conservative Moms for Liberty group, Trump conceded that he lost the 2020 election “by a whisker” — marking one of his most clear public acceptances that he lost the election to Biden. Days later, he once again publicly acknowledged that he did not win the 2020 presidential election, telling podcaster Lex Fridman that he “lost by a whisker.”

In the wake of the 2020 election, Trump and his allies pushed to overturn the election results through phone calls, speeches, tweets and media appearances in six swing states where certified results declared Joe Biden the winner.

Trump most recently began escalating his rhetoric about election fraud when Harris replaced President Joe Biden at the top of the ticket and pulled ahead in some polls. In remarks before the Fraternal Order of Police last week, the former president urged officers to patrol polling places because it would intimidate would-be cheaters.

“I hope you watch for voter fraud,” he said. “Watch for the voter fraud because we win without voter fraud. … You can keep it down just by watching because, believe it or not, they’re afraid of that badge. They’re afraid of you people.”

But while Trump’s post on Saturday falsely claimed that there was “rampant Cheating” in the 2020 presidential race, Trump’s efforts to overturn his loss in the last election faltered in multiple courts when his lawyers and allies could not produce evidence of widespread voter irregularities. In nearly four years since, Trump and his allies have failed to substantiate his claims that he lost the 2020 race due to fraud.

In one of those cases, U.S. District Judge Steven D. Grimberg, whom Trump named to the bench in 2019 in the Northern District of Georgia, wrote that the president’s attempt to block certification of Biden’s win in the state “would breed confusion and potentially disenfranchisement that I find has no basis in fact or in law.”

Election officials who are credibly found to have engaged in criminal activities are already prosecuted in the country. Last month, for example, Tina Peters, a former county clerk in Colorado and Trump ally, was found guilty of seven charges connected to allowing a purported computer expert to copy election data from her office as Trump and his allies searched for evidence to prove their baseless claims of election fraud. Another county election official, Misty Hampton of Coffee County, Ga., faces felony charges along with 14 others, including Trump, for their role in trying to overturn the 2020 result.

And, in the years after Trump began baselessly alleging fraud in the 2020 election, some states such as Iowa, Georgia and Arizona have passed laws beefing up penalties for some election-related offenses despite a lack of evidence that elections in their states were run unfairly. In some cases, these new state election laws effectively criminalize election workers’ errors, raising concerns about the possibility of unfair prosecutions like the kind Trump appeared to describe in his post.

Threats and harassment of election workers have skyrocketed since Trump and his allies began denying the results of the 2020 election, amplifying their false claims on television, podcasts and social media. The developments caused a mass exodus of veteran election administrators from their jobs, and prompted scores of election offices around the country to harden their physical workspaces with bulletproof glass, emergency buttons and extensive crisis training.

Michigan Secretary of State Jocelyn Benson (D), who was directly targeted by armed pro-Trump protesters who gathered outside her home after the 2020 election, on Sunday told The Washington Post that no threats from Trump will dissuade her from performing her duties this election year.

Benson said that her job — and the job of every election official in the country — is to “rise above this noise and focus on continuing to ensure our elections are fair, secure, accessible, and that the results continue to be an accurate reflection of the will of the people.”

Seth Bluestein, a Republican Philadelphia city commissioner, said that every election official he knows “is focused on doing their job well, which unfortunately now also includes preparing for potential threats and violence.”

And Jeff Greenburg, a former director of elections in Mercer County, Pa., said on Sunday that the “continued demonization of election officials is disappointing, disheartening, irresponsible and infuriating.”

“Words matter and this does nothing but potentially put those dedicated public servants in harm’s way. It has to stop,” he said.

On Sunday, North Dakota Gov. Doug Burgum, a Trump campaign surrogate, minimized Trump’s comments in an interview with NBC News’s “Meet the Press,” saying that the former president was “just putting people on notice” that the country must have “free and fair elections.”

But a Republican official in a battleground state who spoke on the condition of anonymity to talk candidly about Trump’s comments found the former president’s post more alarming.

“He sounds like he is losing it,” the Republican official said. “Sad, someone should do something, like replace him as a candidate.”

Toluse Olorunnipa contributed reporting.