US Democrats back Harris as she begins campaigning

Democrats have rapidly coalesced around Vice President Kamala Harris as she raced to secure the party's nomination to take on Donald Trump in November, in the wake of President Joe Biden's sensational exit from the race.

Armed with Biden's endorsement, the 59-year-old won the backing of a flood of Democratic leaders on her first full day of campaigning on Monday.

Ahead of a first trip to campaign headquarters in Wilmington, Delaware, Harris presided over a White House celebration for championship college basketball teams.

She praised Biden as leaving a legacy "unmatched in modern history."

She did not reference her own sudden elevation to presidential candidate in the brief remarks.

But the symbolism of the current vice president having the White House to herself in the absence of Biden, who is nursing a Covid infection at his Delaware beach house, was striking.

Unique opportunity

Earlier, a slew of heavyweight governors, including leaders once seen as potential hopefuls for the party's presidential nomination, added their backing.

"Let's win this," posted Michigan Governor Gretchen Whitmer, announcing her support in tandem with the governors of Illinois, Minnesota and Wisconsin.

The governor of Kentucky, Andy Beshear, also declared his support, making him one of the favourites to be picked as Harris's vice presidential running mate.

Harris must still win over some key hold-outs if she is to wrap up the nomination, which could happen as early as August 1, although some Democrats are still calling for the party to show transparency with an open primary.

America's first female, Black and South Asian vice president has a unique opportunity to unify the party after 81-year-old Biden's historic decision to step aside from the nomination plunged the race into uncharted waters.

Campaign donations

The stunning development has brought a jolt of energy to a demoralised party, transformed an election that threatened to turn into a long slog between two unpopular, elderly men, and could give America its first female president.

Harris's campaign said it had raised a stunning $49.6 million in grassroots donations in less than 24 hours since Biden endorsed her on Sunday.

Harris spent more than 10 hours Sunday placing calls to over 100 party leaders, members of Congress, governors and other figures, a person familiar with her schedule said.

"On each of those calls, the vice president made clear that she... plans to work hard to earn the Democratic nomination," the person said.

She reportedly spoke to former president Barack Obama, one of those who notably has yet to endorse her.

The party has promised a "transparent and orderly process" to replace Biden, who bowed Sunday to Democratic concerns over his age and mental acuity following a disastrous debate performance against former president and Republican candidate Trump in June.