Chicago (AFP) - Kamala Harris is set to deliver the biggest speech of her life Thursday as she accepts the Democratic presidential nomination in Chicago after a historic turnaround in the 2024 White House race.

The 59-year-old US vice president is expected to focus on optimism and her personal story, drawing a contrast with the often dark vision of her Republican rival Donald Trump.

Excitement was already at fever pitch hours before her speech, with delegates clapping and cheering, and special musical guests lined up to perform, including pop star Pink and country band The Chicks.

Speculation swirled about other special guests adding stardust – including possibly mega-star Beyonce, who has provided Harris with her campaign anthem, “Freedom.”

“You know what I’m really excited for?” said Amanda Taylor, a 47-year-old delegate from Missouri. “Of course, Kamala, but I hear maybe Beyonce is going to come!”

Harris has electrified her party and wiped out Trump’s polling lead in the space of a single heady month since President Joe Biden dropped out of the contest, amid fears that at 81 he was no longer capable of running.

In a further sign of the celebratory mood, Harris and her husband, Second Gentleman Doug Emhoff, also swapped messages on X on Thursday for their 10th wedding anniversary.

But Democrats are trying to temper their hopes, knowing that Harris faces a tough sprint to a nail-biting election on November 5, which as in 2020 may be decided by a handful of votes in key states.

From Barack and Michelle Obama to Bill Clinton, senior figures have warned all week that Harris has a brutal fight on her hands to beat 78-year-old Trump.

- ‘Fight for your freedoms’ -

Trump, who believed he was cruising to a stunning return to power against Biden, has been unsettled by the sudden Democratic switch to a much younger woman – and the first Black woman in history to be a major party nominee.

The Republican is increasingly resorting to personal insults and race-baiting.

Speaking near the Mexican border barrier built during his presidency in the battleground state of Arizona, Trump focused Thursday on immigration, which Republicans believe is a major weakness for Harris.

Recounting stories of people he said were killed by migrants who had come across the border illegally, he said: “As Kamala gives her convention speech tonight, she will not mention the victims. She won’t even mention their names.”

The sheer speed of Harris’s rise, from the first female, Black and South Asian vice president to the Democratic standard-bearer also means Harris remains somewhat unknown to US voters.

Harris will seek to remedy that in her speech. She will talk about how she was raised by a working mother and knows the challenges facing families hit by inflation, a campaign official told reporters.

Harris will recount her career as a prosecutor, highlighting her fight for victims of sexual abuse and gun crime, as she faces the first convicted felon ever to seek the US presidency.

Her message will focus on freedoms that she will say Republicans are targeting, especially on restricting abortion and voting rights.

- ‘Kamala vibes’ -

Harris has been short on policy announcements since taking over as the Democratic standard-bearer, particularly when it comes to the economy, a key issue in the election.

“Voters already have the Kamala vibes. Now they need the Kamala agenda,” said Larry Sabato, a professor at the University of Virginia. A lack of economic policy “can defeat her faster than the border,” he added.

For now, Democrats appear happy to ride a tidal wave of joyful vibes. They are unrecognizable from the party that was steeped in despair after Biden’s catastrophic debate performance against Trump.

The Obamas raised the roof in Chicago on Tuesday, with the ex-first lady declaring that under Harris “hope is making a comeback.”

On Wednesday, Clinton and television talk show host Oprah Winfrey were the warm-up acts for Harris’s running mate Tim Walz.

Biden’s farewell address on Monday, when Harris made a surprise appearance on stage to give him a hug, already seems like a distant memory.

After the speech, Harris’s eyes will turn to the sprint for the finish line.

She and Trump are due to hold their first debate on September 10.

Harris is also facing pressure to hold a press conference or interview, having avoided one since rising to the top of the ticket.

Her campaign insists it is taking nothing for granted.

“When you hear the vice president say we’re an underdog…, that’s how we feel about this,” campaign battleground director Dan Kanninen told a Bloomberg news event.