Democrats are readying a rapid-fire response to flood social media and the airwaves with calls for calm and patience with vote-counting should Donald Trump try to prematurely claim election victory, as he did in 2020, Harris campaign and party officials told Reuters.

The Republican candidate told reporters this week that he hoped to be able to declare victory on Election Day, although election experts have cautioned that it could take several days for the final result to be known, especially if there are demands for vote recounts in some key areas. Trump is locked in a razor-thin race with Democratic rival Kamala Harris.

US election winners are typically declared by major media outlets, who analyse vote counts provided by election officials. While candidates sometimes declare victory before those calls are made, it is unusual to do so before the winner is at least arguably apparent.

"We are sadly ready if he does and, if we know that he is actually manipulating the press and attempting to manipulate the consensus of the American people ... we are prepared to respond," Harris said in an interview with ABC on Wednesday.

She gave no details of those preparations, but six Democratic Party and Harris campaign officials said the initial fight against any early Trump victory claim would take place in the court of public opinion. They plan to flood social media and television airwaves with demands that all votes be counted before victories are declared.

"As soon as he (Trump) falsely declares victory, we're ready to get up on TV and provide the truth and tap a broad network of people who can use their influence to push back," a top official with the Democratic National Committee said in an interview.

A senior Harris campaign official said in a conference call with reporters on Friday they "fully expect" that Trump will falsely claim victory on Tuesday night, before all the votes are fully counted.

"He did this before it failed. If he does it again, it will fail," the official said.

In 2020, Trump declared himself the winner in the early morning hours after Election Day, three days before the first television networks made a call. He ultimately lost to his Democratic opponent Joe Biden. He has never accepted the result and continues to falsely assert that it was stolen from him through widespread fraud.

Steve Bannon, a key Trump ally, said Trump should quickly declare victory.

"He should stand up and say, 'Hey, I've won this,'" Bannon told a New York Times reporter on Tuesday, shortly after being released from a federal prison, where he served four months for defying congressional subpoenas on the Jan. 6, 2021 attacks on the US Capitol.

The Trump campaign told Reuters that the Republican candidate would fight for all votes until the polls close, but it did not directly answer a question about whether Trump planned to again declare victory before the race was called.

One Trump donor, Bill Bean, who has at times been critical of the former president, told Reuters he hopes either Harris or Trump win by wide margins, so that the results are as widely accepted as possible.

No Republican firewall

In 2020, Trump's victory declaration was met with condemnation from Democrats and many high-profile Republicans. Markets reacted with a shrug, with major stock indices climbing modestly in the days after the election.

But this time could be different.

The former president has consolidated near-total control of the Republican Party in the intervening years, meaning many influential conservatives could be more willing to go along with his claims, several political strategists said.

"We've seen plenty of evidence that he is in complete control of the party... and we've seen no evidence that party officials or elected officials will push back," said Chip Felkel, a long-time Republican strategist who is critical of Trump.

Trump and his Republican allies have also spent months laying the groundwork for contesting a loss by claiming that non-citizens could try to vote for the Democratic Party and by readying an army of lawyers to go to court to challenge results.

At his rallies, Trump often says they need to make sure their win is "too big to rig."