Given that Donald Trump, her Republican opponent, is expected to win every important battleground state, Kamala Harris's attempt to become America's first female president looks certain to fail.

Although the vice president has not officially conceded, predictions from CBS, the BBC's US partner, indicate that Trump is poised to win a historic triumph.

Harris cancelled her expected election night appearance at Howard University in Washington DC, where she was an undergraduate, after Trump gained momentum as early results began to trickle in.

The Republican subsequently swept the key battleground states of Pennsylvania, North Carolina and Georgia, the BBC's US partner CBS projects.

Trump also looks set to win in other important swing states, including Wisconsin and Michigan.

As expected, Trump has stormed to victory in conservative strongholds from Florida to Idaho, while Harris won liberal states from New York to California, CBS projects.

The Democratic nominee was due to address supporters, but campaign co-chairman Cedric Richmond announced shortly after midnight that she would not attend.

The party-like atmosphere of a few hours earlier at Howard had already turned sour as two swing states were called for Trump.

From Harris HQ, Democratic fundraiser Lindy Li told the BBC that it was "pretty grim right now".

Vice-President Harris, 60, only became the Democratic Party candidate in July, after President Joe Biden withdrew from the race under pressure from within the party. Had she claimed victory, the former California senator have become the first woman, black woman and South Asian-American to win the presidency.

But CBS exit poll data suggests that the Democratic nominee - who campaigned heavily for abortion rights - may have under-performed with women.

Some 54% of female voters cast their ballots for her, the numbers indicate. But Joe Biden won the support of 57% of women in 2020.

Black and Latino voters also appeared slightly less likely to support Harris than they were to back Biden four years ago, according to Associated Press exit poll data.

About 86 million voters cast their ballots early during one of the most turbulent campaigns in recent American history.

The Republican party appears to have enjoyed a resurgence across the country, winning a number of key congressional battles in key states. Control of both the US House and Senate were up for grabs on Tuesday night.

CBS projects Republicans will win control of the Senate after wresting two seats in West Virginia and Ohio from the Democrats and seeing off a stiff challenge in Texas.

Neither party seemed to have an overall edge in the House, which Republicans narrowly control.

If the party does regain control of both chambers, it would make it easier for Trump to push through his agenda - which includes mass deportations of illegal migrants and sweeping tax cuts.

Both sides had armies of lawyers on standby for legal challenges on and after election day.

Philadelphia's police department told BBC Verify it was unaware of any electoral fraud. The city's top prosecutor said the allegation had "no factual basis whatsoever".

Law enforcement agencies nationwide are on high alert for potential violence.

About 30 bomb threats hoaxes targeted election-related locations nationwide on Tuesday, more than half of them in the state of Georgia alone, reports CBS.