Donald Trump on Monday named right-wing Ohio Senator J.D. Vance as his running mate in the US presidential election, rewarding a one-time harsh critic who became one of his most loyal supporters in Congress.

Trump, 78, announced his pick on the first day of the Republican Party convention in Milwaukee, an extravaganza turbocharged by the attempted assassination of the former president.

Seen as the standard-bearer for a new kind of populism that has come to the fore under Trump, 39-year-old Vance embraces the ex-president’s isolationist, anti-immigration America First movement.

One of the least experienced VP picks in modern history, the one-term senator is further to the right than the ex-president on many issues including abortion, where he embraces calls for federal legislation.

He made his name with the 2016 memoir “Hillbilly Elegy,” a best-selling account of his Appalachian family and modest Rust Belt upbringing, which gave a voice to rural, working-class resentment in left-behind America.

Critics have pointed to numerous awkward remarks one-time “Never Trump guy” Vance has made in the past, including calling the billionaire an “idiot,” “noxious” and “reprehensible” and suggesting he was “America’s Hitler.”

Vance reinvented himself as a Trump supporter in recent years and ultimately won the ex-president’s key endorsement in the 2022 Ohio Senate race.

Trump could have dropped his big reveal at any point in the days before Milwaukee, but all his pre-convention plans were upended when a gunman made an attempt on his life at a rally in Pennsylvania Saturday.

‘Supposed to be dead’

With the country still reeling from images of the bloodied Trump being escorted off a rally stage, some 50,000 Republicans descended on the shores of Lake Michigan for the four-day gathering, four months before the election against Democratic President Joe Biden.

The attempted assassination — in which one bystander was killed, and two more wounded — was expected to dominate proceedings, with Trump dismissing calls to postpone and vowing to be “defiant in the face of wickedness.”

“I’m not supposed to be here, I’m supposed to be dead,” he told the New York Post in an interview aboard his plane to Milwaukee, during which he reportedly had a white bandage on his ear and a large bruise on his forearm from where Secret Service agents gripped him.

The Secret Service, which is battling criticism it failed to protect Trump from the shooter, said it was “fully prepared” to ensure security at the convention.

Leading in multiple polls, despite being convicted at his hush-money criminal case in New York, Trump is exuding confidence.

Biden, 81, meanwhile is facing calls from his own side to quit the race over concerns around his age.

Trump scored another victory Monday as a judge dismissed the criminal case against him over accusations he endangered national security by holding on to top secret documents after leaving the White House.

Message of unity

He immediately took to Truth Social to call for the dismissal of all legal cases against him, insisting again that he was being targeted for political reasons.

Trump told the Post he had “prepared an extremely tough speech” about Biden’s “horrible administration” to deliver when he becomes the official Republican nominee on Thursday.

As some Republicans — including Vance — sought to blame Democrats’ anti-Trump rhetoric for the attack, Trump also said he hopes to “unite our country.”

Still, that would see him have to rein in the instinct to settle scores — demonstrated by his cry for supporters to “fight” in the seconds after Saturday’s attack.

The Milwaukee gathering is largely designed in Trump’s image, with digital banners beaming out a message in the cavernous convention arena: “Make America Great Once Again.”

The branding reflects his takeover of the party.

A diminished figure after his 2020 election loss and a subsequent riot at the Capitol by his supporters, Trump has spent much of the last four years reshaping Republican politics.

Installing loyalists including his daughter-in-law Lara Trump atop the Republican National Committee, the billionaire has effectively crushed dissent.

The Milwaukee convention is also a family affair, with Lara and the former president’s two eldest sons, Don Jr and Eric, all due to address delegates. (AFP)

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