CHICAGO, United States (AFP)— Kamala Harris will pledge Thursday to be “president for all Americans” as she accepts the Democratic Party nomination before a rapturous crowd in Chicago in the biggest speech of her life.

A sea of waving Stars and Stripes flags and chants of “USA” filled the arena as jubilant Democrats prepared to anoint Harris as their standard-bearer against Republican Donald Trump.

The 59-year-old vice president was to lay out her personal story and vow a “new way forward” as she reaches out to voters after one of the most extraordinary turnarounds in US political history.

Pop megastar Beyonce, whose song “Freedom” has become the campaign’s anthem, was reportedly set to be a surprise warm-up act before Harris takes her star turn at the Democratic National Convention.

Country act The Chicks sang a version of “The Star-Spangled Banner” while pop star Pink also performed as the Democrats rolled out a list of celebrity backers.

“I know there are people of various political views watching tonight. And I want you to know: I promise to be a president for all Americans,” Harris was to say, according to excerpts released by her campaign.

The first Black woman nominee for a major party, Harris has electrified supporters in the wake of 81-year-old President Joe Biden’s shock decision to drop out a month ago.

She has quickly united the party, wiped out Trump’s lead in the polls, and raised staggering amounts of funds.

“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!”

Biden, who gave an emotional farewell speech to the convention on Monday, said he and First Lady Jill Biden had called Harris to wish her luck.

“I am proud to watch my partner Kamala Harris accept our nomination for president. She will be an outstanding president because she is fighting for our future,” Biden, who is on holiday in California, said on X.

Democrats are however 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 Trump.

Trump, 78, believed he was cruising to a stunning return to power against Biden. Instead he has been unsettled by the sudden Democratic switch to a much younger opponent — and one looking to make history as the first female president.

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