MILWAUKEE: Donald Trump selected US Senator JD Vance on Monday to serve as his vice presidential running mate, as the Republican Party officially nominated the former president as its 2024 presidential nominee at the start of the party's national convention in Milwaukee.

"As Vice President, JD will continue to fight for our Constitution, stand with our troops, and will do everything he can to help me MAKE AMERICA GREAT AGAIN," Trump wrote on his Truth Social platform.

The four-day convention opened in downtown Milwaukee's Fiserv Forum two days after Trump survived an assassination attempt in Pennsylvania, and hours after he secured a major legal victory when a federal judge dismissed one of Trump's criminal prosecutions.

Trump is due to formally accept the party's nomination in a primetime address on Thursday and will challenge Democratic President Joe Biden in the Nov. 5 election.

Trump, 78, and Biden, 81, are locked in what opinion polls show to be a tight election rematch. Trump continues to falsely claim that his 2020 loss to Biden was the result of widespread fraud and has not committed to accepting the results of the election were he to lose.

In the wake of the assassination attempt, Trump said he is revising his acceptance speech to emphasise national unity, rather than highlight his differences with Biden.

"This is a chance to bring the whole country, even the whole world, together. The speech will be a lot different, a lot different than it would've been two days ago," Trump told the Washington Examiner. The would-be assassin's bullet clipped Trump's right ear but did no major harm.

Trump said that following the judge's decision dismissing the documents case, his other outstanding prosecutions should also be thrown out. He is still awaiting trial on two cases - a federal prosecution in Washington and a Georgia state prosecution - for his attempts to overturn his 2020 election defeat.

Both of those cases could be hamstrung by a July 1 US Supreme Court ruling that he has immunity for many actions he took as president.

Trump is due to be sentenced in New York in September for trying to cover up a hush money payment to porn star Stormy Daniels in the weeks before his 2016 election victory.

"This dismissal of the Lawless Indictment in Florida should be just the first step, followed quickly by the dismissal of ALL the Witch Hunts," Trump said on his Truth Social site on Monday, also referencing the prosecutions of hundreds of his supporters who stormed the US Capitol on Jan. 6, 2021.

No place for violence  

Biden has tried to bring the temperature down after months of heated political rhetoric.

"There is no place in America for this kind of violence, for any violence ever. Period. No exceptions. We can't allow this violence to be normalized," Biden said of the assassination attempt in a televised address from the White House on Sunday.

The shooting on Saturday whipsawed discussion around the presidential campaign, which had been focused on whether Biden should drop out due to concerns about his age and acuity following a halting June 27 debate performance.

Nearly two dozen of Biden's fellow Democrats in Congress have called on him to end his reelection bid and allow the party to pick another standard bearer.

The focus this week will be squarely on Trump.

Having consolidated party control, Trump could seize on the prime-time opportunity to deliver a unifying message or paint a dark portrait of a nation under siege by a corrupt leftist elite, as he has done at times on the campaign trail.

Trump has frequently turned to violent rhetoric in campaign speeches, labeling his perceived enemies as "vermin" and "fascists," and accusing Biden without evidence of a conspiracy to undermine the United States by encouraging illegal immigration.

Biden has often warned that a Trump victory would erode US democracy. Some Republicans say those comments helped create the conditions for the shooting.

Investigators say they have been unable to identify an ideology that may have inspired 20-year-old Thomas Matthew Crooks to shoot at Trump from a rooftop outside a campaign event in Butler, Pennsylvania. Though Trump escaped serious injury, a supporter was killed.

Biden ordered an independent review of how the gunman, who was shot dead by agents, could have come so close to killing Trump. Congressional investigators were also due to question the head of the US Secret Service, which is responsible for protecting the former president.

Republicans attending the party's convention said they were not inclined to reassess the party's traditional opposition to firearms restrictions.

“If someone runs someone over with a car, they don’t ban cars," said Melanie Collette, a delegate from New Jersey. "If someone stabs somebody, they don’t ban knives."