Uncertainty reigns entering the final full week of the 2024 US election campaign with Democrat Kamala Harris and Republican Donald Trump locked in a fiercely competitive contest.

What happens in the coming days will be pivotal in deciding the winner of next week’s election.

On Sunday Mr Trump held a rally at Madison Square Garden in New York where several speakers made racist and crude remarks, including comedian Tony Hinchcliffe, who described Puerto Rico as “a floating island of garbage”.

Donald Trump speaking at a campaign rally
Republican presidential nominee Donald Trump speaking at his campaign rally at Madison Square Garden in New York (Alex Brandon/AP)

Shortly after those remarks, Puerto Rican reggaeton artist Bad Bunny endorsed Ms Harris.

Puerto Ricans cannot vote in general elections despite being US citizens, but they can exert a powerful influence with relatives on the mainland.

Ms Harris said Mr Trump’s rally at Madison Square helped prove her point about the stakes of the election.

Speaking to reporters on Monday, Ms Harris said the Sunday event “really highlighted the point that I’ve been making throughout this campaign,” which is that Mr Trump is “fixated on his grievances, on himself, and on dividing our country, and it is not in any way something that will strengthen the American family, the American worker”.

Ms Harris plans to deliver her closing argument on Tuesday in Washington.

Mr Trump plans to hold a rally in Atlanta on Monday evening while Ms Harris will make several campaign stops in Michigan, including a rally with singer-songwriter Maggie Rogers.

US President Joe Biden leaving a polling station
US President Joe Biden leaves a polling station after casting his ballot in New Castle, Delaware (Manuel Balce Ceneta/AP)

US President Joe Biden arrived at a polling station at the Delaware Department of Elections on Monday to cast his ballot early for the November 5 vote.

He chatted to some people in the long line to vote and pushed an older woman in a wheelchair who was ahead of him in line.

American voters are approaching the presidential election with deep unease about what could follow, including the potential for political violence, attempts to overturn the election results and its broader implications for democracy, according to a poll.

The findings of the survey, conducted by The Associated Press-NORC Centre for Public Affairs Research, speak to persistent concerns about the fragility of the democracy, nearly four years after former president Mr Trump’s refusal to accept the 2020 election results inspired a mob of his supporters to storm the US Capitol in a violent attempt to stop the peaceful transfer of power.

About four in 10 registered voters say they are “extremely” or “very” concerned about violent attempts to overturn the results after the November election.

A similar share is worried about legal efforts to do so. And about one in three voters say they are “extremely” or “very” concerned about attempts by local or state election officials to stop the results from being finalised.

Authorities were investigating on Monday after early morning fires were set in ballot drop boxes in Portland, Oregon, and in nearby Vancouver, Washington, where hundreds of ballots were destroyed.

The Portland Police Bureau reported that officers and firefighters responded to a fire in one ballot drop box at about 3.30am and determined an incendiary device had been placed inside. Multnomah County elections director Tim Scott said a fire suppressant inside the drop box protected nearly all the ballots and only three were damaged.

A few hours later, across the Columbia River in Vancouver, television crews captured footage of smoke pouring out of a ballot box at a transit centre.

Police said they have identified a “suspect vehicle” connected to incendiary devices that set the fires.

Surveillance images captured a Volvo stopping at a drop box in Portland, Oregon, just before security personnel nearby discovered a fire inside the box.