Joe Biden's withdrawal upends what was already a White House race for the ages, but it will rattle Donald Trump, too -- forcing him to recalibrate a campaign that was focused almost entirely on his former opponent.

For months Trump and his allies have been playing on concerns that the 81-year-old Biden may no longer be fit for office, gleefully sharing video clips of every stammer, rhetorical gaffe and red carpet stumble.

He was frequently a target of Republican mockery and scorn at the Republican National Convention in Milwaukee, where Trump's newly announced running mate J.D. Vance called him "Fake Scranton Joe."

But with the Democrat no longer in the race, the Trump operation finds itself pushed into a strategic pivot, forced now to shift its messaging to fit a contest with no incumbent and a yet-to-be-confirmed opponent, although Biden did endorse Vice President Kamala Harris on Sunday as he pulled out of the race.

"Biden withdrawing is bad news for Trump," Henry Olsen, a senior fellow at the conservative Ethics and Public Policy Center think tank, told AFP.

"Biden has the lowest job approval of any first-term president at this stage of his presidency in polling history and is also irretrievably........

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