(UPDATES) MILWAUKEE, United States — Donald Trump predicted an "incredible victory" Thursday in accepting the Republican presidential nomination from a party euphoric over his escape from assassination and buoyed by the apparent implosion of Joe Biden's reelection campaign.

"We will have an incredible victory, and we will begin the four greatest years in the history of our country," Trump said at the Republican convention in Milwaukee.

It was his first speech since a 20-year-old man shot at him, causing a slight injury to one ear, but killing a bystander, during a rally last weekend.

"I am running to be president for all of America, not half of America, because there is no victory in winning for half of America," Trump said, still sporting a bandage over his ear.

Trump — expected to speak for around 90 minutes — took the stage to chants of "USA" from a crowd members of which have talked of him in divine terms.

Warm-up acts included shirt-ripping 1980s wrestling icon Hulk Hogan and conspiracy theorist and far-right media guru Tucker Carlson, who described Trump's survival as a historic moment.

At the assassination attempt, Trump became "leader of a nation," Carlson said.

Trump, 78, has put behind him a torrent of scandals, his unprecedented attempt to overturn his 2020 election loss to Biden, and his 34 felony convictions in May at a New York criminal trial.

Now, with Republicans more united behind him than ever, he is increasingly bullish about a shock return to power.

On Friday, Biden, 81, looked close to being forced by his own Democratic Party to withdraw and make way for Vice President Kamala Harris or another candidate, as fears spiral that his faltering physical health will lead to a loss in November.

Senior Trump adviser Jason Miller told AFP that "nothing fundamentally changes" for Trump if Biden drops out.

Trump's family was in attendance, with son Eric rousing the crowd into a chant of "fight, fight, fight!" Trump's wife Melania, who has been mostly absent throughout the campaign, arrived to applause but did not speak — a remarkable break with US political convention at such events.

Supporters have been lining up all week to applaud the former president for his bravery since the weekend attack by a gunman at a Pennsylvania rally.

Others addressing the convention included Trump's longtime friend Dana White, chief executive of the Ultimate Fighting Championship. Trump has attended multiple UFC bouts as he seeks to lock in younger male voters.

Striking a different tone, evangelist preacher Franklin Graham — whose father was spiritual adviser to multiple US presidents — led a lengthy prayer for Trump.

With Biden still reeling from the aftermath of his disastrous debate performance against Trump last month, polls show a gap gradually opening in the long-close race.

The Republican campaign has even been talking up Trump's chances in Democratic strongholds like Minnesota and Virginia, potentially forcing Biden's funds and manpower away from defending his "blue wall" in Michigan, Pennsylvania and Wisconsin.

The four-day party convention opened Monday after Trump won almost every state's primary contest. The aura of festive unity is in marked contrast to a 2016 edition hampered by party divisions and a second appearance in 2020, reined in by the Covid-19 pandemic.

The schedule was designed around his image, with themes for each day playing on his "Make America Great Again" rallying cry.

The week also saw Trump name right-wing Sen. J.D. Vance of Ohio as his running mate.

The 39-year-old author of "Hillbilly Elegy," a best-selling memoir about growing up poor in working-class America, is a former Trump critic who became one of his staunchest backers.

Trump himself appeared a spent force after his 2020 election loss, his refusal to accept the results, and the assault by his supporters on the US Capitol in an attempt to stop certification of the vote.

However, he has since reshaped the Republican Party in his own image, installing close allies in key positions — including his daughter-in-law Lara Trump on the Republican National Committee — and crushing dissent.