Washington (AFP) - Kamala Harris hits the US campaign trail Tuesday after effectively clinching the Democratic presidential nomination, heading to the battleground state of Wisconsin to renew her attacks on Republican candidate Donald Trump.

The vice president took just 36 hours to secure enough delegates to be nominated, moving with lightning speed after President Joe Biden’s exit from the race triggered one of the largest election upheavals in modern US history.

Top Democratic congressional chiefs – Senator Chuck Schumer and House minority leader Hakeem Jeffries – threw their weight behind her in a press conference.

Hollywood star George Clooney – who made waves earlier this month as one of the first high-profile Democratic activists to urge Biden to drop his reelection bid – also said he is now behind 59-year-old Harris’s campaign to face Trump in November.

On her trip to Milwaukee, Harris was expected to launch another attack on convicted felon Trump as she leans into her past role as California’s top prosecutor.

“She is prepared to prosecute the case against Donald Trump,” said Wisconsin campaign spokeswoman Brianna Johnson.

- ‘Saving democracy’ -

US media reported that Harris late Monday sailed past the minimum number of delegates needed to become presumptive nominee – 1,976 out of nearly 4,000.

Harris, bidding to become the first female, Black and South Asian vice president in US history, said in a statement that she was proud and looks forward to accepting the nomination.

That should come by August 7 in an online vote of delegates nearly two weeks before the formal Democratic convention in Chicago.

Support continued to pour in with the United Steelworkers Union and philanthropist Melinda French Gates, the ex-wife of Microsoft co-founder Bill Gates, both endorsing.

Harris’s campaign also announced it had raised $100 million since her entry into the White House race, with 62 percent of donations coming from first time donors.

Biden stunned the world by dropping his reelection bid Sunday, bowing to weeks of pressure after a disastrous debate performance against Trump.

Having made the announcement in a social media post while recovering from Covid at his Delaware beach house, Biden has yet to speak at length about his decision.

Biden was due back at the White House Tuesday after his doctor said he was now all clear from Covid. Biden announced he will deliver a primetime speech from the Oval Office on Wednesday about “what lies ahead.”

- ‘Brilliant young man’ -

Former president Trump – who survived an assassination attempt on July 13 – continued to relentlessly slam both Harris and Biden.

Trump late Monday branded her “Lyin’ Kamala Harris” and said she had “terrible” poll numbers against a “fine and brilliant young man named DONALD J. TRUMP! Be careful what you wish for Democrats???”

But recent polls have shown Harris roughly neck and neck with 78-year-old Trump, whose campaign has been forced into a drastic rethink now that Biden’s departure has made him the oldest nominee in US political history.

Harris’s selection of Milwaukee for Tuesday’s rally is no accident – last week, the city played host to the Republican National Convention, where Trump was nominated as the party’s official candidate for president.

With America’s role as a world power under scrutiny amid the political chaos, Biden and Harris will meanwhile also have to deal with a major foreign policy headache this week.

They are due to hold separate meetings with Israeli Prime Minister Benjamin Netanyahu as he visits Washington, with Biden saying he will spend his remaining time in office working to end the war in Gaza.

Harris said she would not attend Netanyahu’s address to the US Congress on Wednesday due to a pre-planned rally, but an aide said this “should not be interpreted as a change in her position with regard to Israel.”