In the latest blow to US President Donald Trump’s attempts to cling to power, cracks have emerged between two of his key legal allies, William Barr and Rudy Giuliani.

Mr Barr, the US Attorney-General, announced on Tuesday (Washington time) that no evidence of widespread voter fraud had been found, contrary to Mr Trump’s repeated allegations the November 3 election was rigged.

It’s a dramatic backdown. Mr Barr has been a key supporter of the President, even calling for an investigation to “pursue substantial allegations of voting and vote tabulation irregularities” in November.

At the time, Democrats and President-elect Joe Biden’s campaign condemned accused Mr Barr of fuelling just the kind of far-fetched claims he should have been guarding against.

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But Mr Barr appears to have changed his mind, after probes turned up no evidence to support claims of “substantial” fraud. He said US attorneys and FBI agents had followed up specific complaints – but uncovered nothing that would change the election outcome.

“To date, we have not seen fraud on a scale that could have affected a different outcome in the election,” he said.

Despite that, Mr Giuliani has not given up the fight, vowing to continue what he says is the “pursuit of truth” – searching for evidence to overturn Mr Biden’s win.

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Mr Giuliani, who is leading Mr Trump’s legal fight, blasted Mr Barr, accusing him of failing to properly investigate evidence of widespread voter fraud he claimed they had uncovered.

“With all due respect to the Attorney-General, there hasn’t been any semblance of a Department of Justice investigation,” Mr Giuliani, a former federal prosecutor, and colleague Jenna Ellis said in a joint statement.

Mr Barr also revealed on Tuesday that he had elevated Connecticut federal prosecutor John Durham to the status of special counsel.

Mr Durham will investigate the origins of the US government’s own probe into the role of Russia in Mr Trump’s 2016 election win.

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Mr Durham’s appointment gives him more independence, subjecting him to the same rules that governed the May 2017 appointment of Robert Mueller to investigate whether Mr Trump’s campaign colluded with Russia.

Mr Durham will continue to investigate whether top Obama-era intelligence and law enforcement officials committed crimes when they launched a probe into the 2016 Trump campaign.

The appointment took effect on October 19.

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Mr Biden beat Mr Trump in the November 3 poll by a wide margin of 306-232 votes in the Electoral College vote that chooses the president, as well as by more than 6.2 million ballots in the popular vote.

Despite that, Mr Trump has repeatedly claimed – without offering evidence – that the election was marred by widespread fraud. The claims have been repeatedly rejected by state and federal officials.

His campaign has also pursued legal challenges to election results in numerous states. None has yet resulted in any meaningful gains for the President.

In fact, a recount in Wisconsin, prompted by Mr Trump’s demands, only served to increase Mr Biden’s lead in that state.

Judges have rejected most of the lawsuits, expressing scepticism about claims that the election results are illegitimate.

Mr Trump and his team have actively promoted their allegations via social media.

Countless tweets on the President’s account have been flagged by Twitter for containing “disputed” claims about election fraud – or misinformation.

In November, Mr Barr told federal prosecutors to pursue investigations into credible allegations of election fraud, but warned them to avoid probes into “fanciful or far-fetched claims”.

In the nearest he has come to a concession, Mr Trump said last week that he would depart the White House if the Electoral College declares Mr Biden the election winner.

Asked if he would leave the White House if the college vote went against him, Mr Trump said: “Certainly I will. And you know that.

“If they do, they made a mistake.”

The Electoral College will meet on December 14.

-with AAP