More than half of Republican voters surveyed said they would be in favour of suspending the 2020 election if Donald Trump asked for more time to weed out illegal voters, a new poll shows.

According to the poll, run by two academic researchers and published in the Washington Post, 52 per cent of those Republicans would agree with postponing the election if the President felt it was necessary.

That bumps up to 56 per cent if Republicans in Congress were behind the action as well.

The poll was conducted between 5 June and 20 June, comprising interviews of 1,325 Americans, with 650 self-identifying as Republicans.

Following the election, Mr Trump has repeatedly said "millions of illegal votes" were cast during the election, but no proof has been presented to the public.

He has even established the Presidential Commission on Election Integrity, led by Vice President Mike Pence and Kansas Secretary of State Kris Kobach.

He has also repeatedly claimed that voter fraud was a problem and benefited Hillary Clinton - she won the popular vote by three million ballots - despite his win. He said "we have a lot to look into" regarding the deceased, illegal voting by immigrants and undocumented persons and voters registered in multiple states.

However, several studies and analyses done by universities and the nonpartisan Government Accountability Office all said the same thing: voter fraud or impersonation of voters is extremely rare.

Despite all the evidence, 47 per cent of the Republicans surveyed think Mr Trump actually won the popular vote and an overwhelming 73 per cent think "voter fraud happens somewhat or very often".

A majority, 68 per cent, also believe that "millions of illegal immigrants voted."

In terms of how this support breaks down, it is "more prevalent among Republicans who were younger, were less educated, had less factual knowledge of politics and strongly identified with the party."