Trump’s repeated claims that his defeat would only result from voter fraud may fuel doubts over election legitimacy and motivate supporters to surveil polls

Donald Trump’s claims that if he loses in November it will be due to a “rigged” election have sparked strong bipartisan criticism from election lawyers, donors and a former member of Congress who warn that the Republican candidate’s words are dangerous, fueling doubts about the election’s legitimacy and potentially leading to voter intimidation.

As his poll numbers have weakened and his high-decibel spats with critics escalated, Trump has raised the specter of rigged elections and suggested that if he loses it might well be because of voter fraud.

“The only way we can lose, in my opinion, I really mean this, Pennsylvania, is if cheating goes on,” Trump told a largely white rally last month in Altoona, Pennsylvania. “Go down to certain areas and watch and study [to] make sure other people don’t come in and vote five times.

“We’re going to have unbelievable turnout, but we don’t want to see people voting five times,” Trump added, saying that he had “heard some stories about certain parts of the state and we have to be very careful”.

Several election lawyers and analysts are disturbed by Trump’s combustible use of language.

“Trump’s rhetoric is troubling and casts a shadow over the legitimacy of the elections,” said Ken Gross, a well-known election lawyer in Washington who represents both Republican and Democratic clients. “Trump’s words may motivate people to go to polling places and potentially intimidate people not to vote.”

The idea that “elections are rigged and there’s widespread fraud is not backed up by facts”, he said.

Others echo these concerns. “To argue that the process is rigged and prepare people for a supposedly illegitimate outcome is a very dangerous thing,” former Reublican representative Vin Weber told the Guardian. “What you want is to have a civil peaceful election [and] you don’t want to disrupt that.”

One prominent GOP election lawyer says that Trump’s fears are overblown, stressing that the “far right has been worked up about voter fraud for the last five to 10 years, but there’s little evidence that this type of activity is material. I don’t like it when people talk about issues that haven’t happened yet, or are phantom issues”.

Recent studies indicate that voter fraud is not widespread. Only 31 cases of possible in-person voter fraud were found from 2000 to 2014, during which period over 1bn votes were cast in general and primary elections, according to a study by Justin Levitt, a professor at Loyola Law School.

Nonetheless, Trump’s ominous warnings seem part of a new campaign mantra. The candidate voiced similar views this summer in an interview with The Washington Post and on Fox News with Sean Hannity.

Trump complained to the Post that recent court decisions nixing restrictive voter ID laws could well lead to voter fraud, calling this a “very unfair development. We may have people vote 10 times”. Likewise on Hannity, Trump urged supporters to begin “watching closely” lest the election be “taken away from us”.

On the campaign trail in Ohio Trump declared: “I’m afraid the election is going to be rigged. I have to be honest.”

Moreover, the candidate’s website boasts a section that not only informs supporters how they can be a “volunteer Trump election observer”, but also echoes Trump’s heated rhetoric about election rigging. Those who sign up to be volunteers receive emails explaining that the campaign intends to do “everything that we are legally allowed to do to stop crooked Hillary from rigging the election”. The website notes that volunteers would be useful in Ohio and Pennsylvania.

There is nothing wrong with Trump talking about training poll watchers as campaigns have long done, stresses Larry Noble, a former general counsel at the Federal Election Commission who now holds the same title at the nonpartisan Campaign Legal Center. “But if he’s suggesting, as it appears he is, that his supporters should take any actions that would result in intimidation of voters, that’s illegal.”

Adds Charlie Black, a veteran GOP operative: “If it was my campaign, I’d let the lawyers handle any potential voter fraud.”

Some conservative groups have echoed Trump’s fears about rigged elections.

Right-leaning groups – including Judicial Watch and True the Vote – are calling for extra vigilance, and raising money off the issue. Judicial Watch has rolled out an “Election Integrity Project” which warns voters that “the integrity of our elections is under systematic assault by leftists and politicians whose objective is clearly to manipulate the elections for their own gains”. The project charges that certain states are refusing to clean their voter rolls of the deceased and people who have moved and has filed suits in some states to force them to do so.

Outside experts disagree with the premise that there’s a link between voter rolls and voter fraud. “In-person voter fraud is virtually nonexistent and is a myth that has been used to to justify voter restrictions like photo IDs,” said Gerry Hebert, the executive director of the Campaign Legal Center.

And Hebert adds that filing a lawsuit to clean up voter rolls “is not proof of voter fraud”.

But Trump allies have continued to stoke fears of fraud. Longtime Trump confidante Roger Stone, who has offered periodic advice during the campaign and publicly raised the specter of a rigged election, told Breitbart News that the government “will be shut down if they attempt to steal this election and swear Hillary in”.

Some GOP operatives poke fun at Trump’s fears of a “rigged” election – especially in Pennsylvania.

“Trump’s comments make perfect sense coming from a paranoid narcissist,” quipped Rick Tyler, a former spokesman for Senator Ted Cruz, noting that the GOP “hasn’t won Pennsylvania in a presidential election since 1988”.

But other critics see graver threats in Trump’s words.

“If people start to believe that elections aren’t legitimate then it could encourage anarchy and despotism,” said Michael Epstein, a GOP donor and fundraiser who initially backed Governor Scott Walker in the primaries. “If you lose respect for government, anything is possible.”