Biden goes from star to sideshow at Democratic convention

A few short weeks ago, Joe Biden was set to headline the Democratic National Convention -- but after a brutal political comedown, he's now the warm-up act for Kamala Harris.

For a proud man like the 81-year-old US president, his speech on the first day of the party's gathering in Chicago on Monday is sure to come with conflicting emotions.

Still harboring frustration over his exit from the White House race, Biden will be trying to balance his feelings with the need to help his vice president beat Republican Donald Trump in November.

With Harris set to formally accept the Democratic presidential nomination on Thursday, Biden's appearance was going to be like "opening for Taylor Swift," said Brookings Institution senior fellow William Galston.

"This will not be an easy speech," Galston told AFP.

But like all US presidents, Biden has an eye on the history books, and he'll know that the surest way to secure his legacy now runs through Harris.

"I'm sure he understands that the chances that his presidency will be regarded as successful go way up if Kamala Harris succeeds him," said Galston.

- 'The worst night' -

Trump has wasted no time in mocking the fact that his former opponent no longer has top billing.

"Monday, that's the worst day," Trump told a rally on Wednesday. "They're not even giving him a good spot to speak."

The former president also accused Harris of "trying to throw him (Biden) overboard."

Biden has deliberately taken a back seat to Harris since his stunning July 21 decision to bow out of the race following a catastrophic debate against Trump.

As Harris reenergizes the Democratic Party, Biden has spent long spells at his Delaware holiday home, where he was spotted cycling and relaxing on the beach with his family this past weekend.

And at times he has made light about the sudden end of his five-decade political career.

"I invited you to the White House because I'm looking for a job," Biden joked with influencers at an event on Wednesday.

But there have been flashes of frustration too.

Biden is reportedly angry at former US House Speaker Nancy Pelosi's role in pushing him out, and disappointed that former president Barack Obama didn't do more to support him.

Acknowledging that Congressional Democrats feared Biden would harm their own electoral chances in November, Biden told CBS on Sunday that "I was concerned if I stayed in the race, that would be the topic."

"You'd be interviewing me about 'why did Nancy Pelosi say…' 'why did so-and-so…' -- and I thought it'd be a real distraction."

- 'At peace' -

Biden is expected to head off on holiday straight after his convention speech, sparing him the sight of thousands of delegates cheering the newly anointed Harris as the balloons fall.

Despite all that, Biden will still be welcomed by the party in Chicago. He will have a crucial role in pursuing the goal that he says was at the heart of his decision -- beating Trump.

"With some reflection, particularly if they win, he could come to a really comfortable position with his legacy and his decision," Casey Burgat of George Washington University told AFP.

His challenge will now be to give a speech that helps Harris, without burdening her with too much of his own administration's baggage.

The 59-year-old vice president is keen to blaze her own path, particularly on the issue of the economy, one of the areas that hit Biden's popularity hardest.

For Biden, it will be more of a valedictory turn.

"Maybe we'll see a Biden who is closer to being at peace with all of this than we might imagine," said Galston.

Biden is also expected to emphasize the idea of moving to a new generation -- especially since it is Republicans, with the 78-year-old Trump, who now have the oldest candidate in US history.

With Harris having wiped out Trump's lead in the polls, Democrats already view Biden more favorably than when he was their standard-bearer.

"He can expect a much warmer reception than if he'd stayed on, frankly," said Galston.