WASHINGTON — About half of all Republicans believe president Donald Trump "rightfully won" the US election but that it was stolen from him by widespread voter fraud that favoured Democratic president-elect Joe Biden, according to a new Reuters/Ipsos opinion poll.

The Nov 13-17 opinion poll showed that Mr Trump’s open defiance of Mr Biden's victory in both the popular vote and Electoral College appears to be affecting the public’s confidence in American democracy, especially among Republicans.

Altogether, 73 per cent of those polled agreed that Mr Biden won the election while five per cent thought Mr Trump won. But when asked specifically whether Mr Biden had "rightfully won," Republicans showed they were suspicious about how Biden's victory was obtained.

Fifty-two percent of Republicans said that Mr Trump "rightfully won," while only 29 per cent said that Mr Biden had rightfully won.

Asked why, Republicans were much more concerned than others that state vote counters had tipped the result toward Mr Biden: 68 per cent of Republicans said they were concerned that the election was "rigged," while only 16 per cent of Democrats and one-third of independents were similarly worried.

Even before winning the 2016 election, Mr Trump kept up a drumbeat of complaints about the process, claiming without evidence that it was unfair to him.

Since Mr Biden amassed enough electoral votes to win the White House on Nov 7, Mr Trump has ramped up those criticisms, telling his supporters that he is the victim of widespread illegal voting.

Mr Trump has failed to give any proof for his claims and has not been able to back them up in court, however. Republicans announced this week that they were dropping federal election lawsuits in Michigan, Georgia, Pennsylvania and Wisconsin.

The poll showed that more Americans appear to be more suspicious about the US election process than they were four years ago.

Altogether, 55 per cent of adults in the United States said they believed the Nov 3 presidential election was "legitimate and accurate," which is down seven points from a similar poll that ran shortly after the 2016 election. The 28 per cent who said they thought the election was "the result of illegal voting or election rigging" is up 12 points from four years ago.

The poll showed Republicans were much more likely to be suspicious of Mr Trump's loss this year than Democrats were when Ms Hillary Clinton lost four years ago.

In 2016, 52 per cent of Democrats said Hillary Clinton's loss to Trump was "legitimate and accurate," even as reports emerged of Russian attempts to influence the outcome. This year, only 26 per cent of Republicans said they thought Trump's loss was similarly legitimate.

The Reuters/Ipsos poll was conducted online, in English, throughout the United States. It gathered responses from 1,346 respondents, including 598 Democrats and 496 Republicans, and has a credibility interval, a measure of precision, of five percentage points. REUTERS