Washington DC - He still refuses to acknowledge his defeat four years ago, so it is no great surprise that Donald Trump is laying the groundwork to contest another election if he loses again.

But the stream of ambitious Republicans joining him in declining to commit to the outcome is raising concerns of a repeat of the chaos around 2020 as America prepares for a rematch between Trump and Joe Biden in November.

Many have designs on the vice president's job, including Florida Senator Marco Rubio, who told NBC on Sunday he would not accept an "unfair" election and accused Democrats of having "opposed every Republican victory since 2000."

Rubio was referring to the grudging reactions to their defeats of the John Kerry and Hillary Clinton camps in 2004 and 2016 – but both candidates conceded in a timely fashion and made way for peaceful transfers of power.

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Trump claimed that the 2020 election was "rigged" and spearheaded a concerted campaign to sow doubt about his loss to Biden via multiple baseless conspiracy theories that inspired the storming of the US Capitol by his supporters.

Years of investigation and more than 60 lawsuits uncovered no evidence of significant malpractice, yet as recently as Friday, Trump claimed falsely that he had won a "landslide" in Minnesota, a state he lost by more than 200,000 votes.

Meanwhile, the alleged criminal scheme to overturn the 2020 result that ran parallel to Trump's deluge of misinformation has landed him with federal and state indictments on felony charges including conspiracy, obstruction, and racketeering.

Adopting the same posture for 2024, he has refused to commit to honoring the outcome in series of interviews.

Trump told The Milwaukee Journal-Sentinel earlier in May that he would accept the election results "if everything's honest" – adding that he would "fight for the right of the country" if he suspected fraud.

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Questions from the media about accepting election results are a new thing, as it was a given before the Trump era that candidates voicing unqualified support for democracy would bolster rather than harm their political ambitions.

But multiple Republican vice-presidential hopefuls have struggled to walk the line between upholding democracy and keeping Trump onside, preferring to hedge on whether they will accept November's result as binding.

House Republican conference chairwoman Elise Stefanik, an outside bet for the Trump ticket, was the first of his potential running mates to refuse to say whether she would vote to certify the results of the 2024 election.

She claimed in January that she would only accept a "legal and valid election," although – like Rubio – she didn't define her terms.

Neither did Ohio Senator J.D. Vance, another hardline conservative on the shortlist for the vice president's job, who told CNN he would accept the results only if the vote was "free and fair."

Vance's fellow senator Tim Scott, another frontrunner in the "veepstakes," was repeatedly pressed in an NBC interview to say whether he would accept November's results and refused.

And North Dakota Governor Doug Burgum – who, along with Scott, was defeated by Trump in the Republican presidential primary contest but has since found favor – has similarly hedged on the issue.

Charlie Kolean, the chief strategist at conservative political consultancy RED PAC, said Republicans in Trump era would – and should – continue to position themselves as the party of "election security and integrity."

"It is crucial for these candidates to become recognized authorities in areas that resonate with voters, as this will strengthen the GOP ticket heading into November," he told AFP.

But political scientist Nicholas Creel, of Georgia College and State University, said the obfuscation reflects that Republicans simply cannot acknowledge Trump's 2020 defeat without jeopardizing their standing in the party.

"The party is no longer tied to ideology but idolatry, making it more akin to a cult than a modern political party," he said.