Two in Five US Voters Worry about Intimidation at Polls: Reuters/Ipsos

So far no violence has been reported at any early voting centers or ballot drop-off locations ahead of the Nov. 8 elections, when Republicans are favored to win control of the US House of Representatives and possibly the Senate.

But officials in Arizona, a key battleground, have already asked the federal government to probe a case of possible voter intimidation, after people casting ballots were conspicuously filmed and followed.

An official complaint noted that the self-appointed monitors called the voters "mules," a reference to a conspiracy theory popularized by supporters of former president Donald Trump's false claim that his 2020 defeat was the result of widespread fraud.

The Reuters/Ipsos poll, completed on Monday, also found that two-thirds of registered voters fear that extremists will carry out acts of violence after the election if they are unhappy with the outcome.

The findings illustrate what some observers have said is growing evidence of a lack of trust in the nation's democratic institutions, following decades of deepening partisanship.

Kathy Boockvar, a former top election official for Pennsylvania, said fears of voter intimidation and violence run counter to American tradition.

"Our country is based on democracy. We should be excited about Election Day," said Boockvar, a member of the bipartisan Committee for Safe and Secure Election.

Distrust between America's two political camps has grown over the last half century, with bipartisan legislation becoming rarer and a growing share of parents saying they would be displeased if their child married someone from the other political party.

Among the registered voters polled by Reuters/Ipsos, 43% were concerned about threats of violence or voter intimidation while voting in person. The fear was more pronounced among Democratic voters, 51% of whom said they worried about violence, although a still-significant share of Republicans - 38% - harbored the same concerns.

About a fifth of voters - including one in 10 Democrats and one in four Republicans - said they were not confident their ballots would be accurately counted.

Fired up by his false fraud claims, thousands of Trump supporters stormed the Capitol on Jan. 6, 2021.

While voter rights advocates accuse far-right groups who believe those claims of sending poll watchers to intimidate minority voters aligned with the Democratic Party, US conservative media highlight left-wing violence, frequently tying Democrats to riots sparked by the 2020 murder of George Floyd, a Black man, by a white police officer in Minneapolis.

Some two-thirds of registered voters - 67% - said they were concerned extremists will commit acts of violence after the election, including about three in four registered Democrats and three in five registered Republicans.

More than 10 million people have already cast ballots in the contests that will shape the rest of Democratic US President Joe Biden's term.

Republican control of either chamber of Congress would effectively torpedo Biden's agenda.

About two-thirds of Republicans and one-third of Democrats think voter fraud is a widespread problem, the Reuters/Ipsos poll found. Two-thirds of Republicans think the 2020 presidential election was stolen from Trump.

Trump's claims of fraud were dismissed by dozens of US courts, state reviews and multiple members of his administration. Nonetheless, they have found widespread acceptance, helping fuel a cottage industry of poll-watching tools.

One software application heavily promoted by far-right media organizations lets users view a map of reported polling station problems and abnormalities in vote counts. Conservative activists have set up a hotline to collect similar reports.

The Reuters/Ipsos online poll gathered responses from 4,413 US adults nationwide and had a credibility interval, a measure of precision, of between 2 and 5 percentage points.