Washington (AFP) - Kamala Harris and Donald Trump are entering the final one-month sprint to the most dramatic US presidential election in modern history, with both candidates warning the fate of a divided nation hangs on a result that is still too close to call.

The 2024 race has seen more twists than a Hollywood blockbuster, from the vice president’s shock replacement of Joe Biden as the Democratic nominee, to the Republican former president riding out two assassination attempts as he eyes a sensational comeback to the White House.

Now the United States is bracing for a cliffhanger ending with Trump, 78, and Harris, 59, neck-and-neck in the polls – and the Republican warning darkly of a repeat of the chaos that followed the 2020 election if he does not win this time around.

The world is meanwhile waiting with bated breath to see who ends up in the Oval Office, at a time when the Middle East slips ever closer to all-out war and Ukraine’s fight for survival against Russia hinges on the US support that Trump has previously criticized.

“This is a tremendously important election,” Peter Loge, director of George Washington University’s School of Media and Public Affairs, told AFP.

“They (Trump and Harris) have both cast it in apocalyptic terms.”

- Stark contrast -

One thing is for sure: the next four weeks will see Harris and Trump – along with their running mates, Democratic Minnesota Governor Tim Walz and Republican Ohio Senator J.D. Vance – relentlessly hitting the campaign trail.

America’s idiosyncratic electoral college means they will end up fighting for a few thousand votes in seven key swing states that are expected to decide the election – Arizona, Georgia, Michigan, Nevada, North Carolina, Pennsylvania and Wisconsin.

And as America decides, Harris and Trump will be offering voters two starkly different visions.

With her slogan “We’re Not Going Back,” Harris promises to turn the page on an era of divisive politics. Trump pledges to “Make America Great Again” as he paints a picture of a dystopian nation that only he can fix.

In Harris, Democrats have a candidate who has smashed glass ceilings as America’s first female, Black and South Asian vice president, and who promises to fight for abortion rights and what she calls an “opportunity economy.”

But her meteoric rise means her character and policies remain an unknown quantity to many voters.

Trump is the first convicted felon to run for president, but one whose right-wing base laps up his insults of “Comrade Kamala,” and his promises to boost the economy and lock up his political opponents.

Above all, he is hoping that the explosive issue of migration will help him win, with the billionaire doubling down on harsh rhetoric accusing migrants of “poisoning” American blood.

“Vice President Harris and Governor Walz are saying the American story is complicated, but we can make this right,” said Loge.

Trump meanwhile had a “very compelling story… give the strongman a chance, let him clear the deck, we’ll come back to democracy later. The problem is we can never come back to democracy.”

- ‘Pass the torch’ -

US voters have also had to get their heads around a completely upended race.

Less than three months ago, they still faced a deeply unpopular rematch between Trump and the 81-year-old Biden for the title of America’s oldest president.

Everything changed in the space of 90 stunning minutes as Biden imploded in his debate against Trump, crystallizing years of Democratic fears about his age.

A month later, Biden dropped out, saying it was time to “pass the torch” to Harris.

With dizzying speed, Harris wiped out Trump’s lead in the polls, fired up huge rallies and raised piles of cash.

The Republican suddenly found himself facing a much younger – and female – candidate.

The turnaround was especially abrupt for Trump, coming just eight days after gunman opened fire at a rally in Butler, Pennsylvania, wounding the Republican in the ear.

Harris however insists she remains the “underdog” and the polls predict a nail-biting race.

A result could also take days or weeks if there are disputed counts or legal challenges as expected – meaning the US election cliffhanger could last into January.