Democratic presidential nominee US Vice President Kamala Harris boards Air Force Two at Wilkes-Barre Scranton International Airport in Scranton, Pennsylvania on November 4, 2024. [AFP]

Bitter rivals Kamala Harris and Donald Trump embark on a final frenzied campaign blitz Monday with both hitting must-win Pennsylvania on the last day of a tight and volatile US presidential election campaign.

Republican Trump has promised a “landslide” as he seeks a sensational return to the White House, while Democrat Harris said the “momentum” was on the side of her bid to be America’s first woman president.

But the polls suggest a different story on the eve of Election Day -- total deadlock in surveys nationally and in the seven swing states where the result is expected to be decided.

The world is anxiously watching the election, which is set to have profound implications for conflicts in the Middle East and Russia’s war in Ukraine, and for tackling climate change.

Now a race of dramatic twists, including two bids to kill Trump and Harris’s shock late entrance, is coming down to the most viciously fought-over battleground.

Harris will spend the whole day campaigning in the rust-belt state of Pennsylvania, culminating in a huge rally in Philadelphia featuring singer Lady Gaga. Trump will travel to North Carolina, Pennsylvania and then Michigan.

In a sign of how crucial Pennsylvania is to occupying the Oval Office, Trump and Harris will hold dueling rallies in the industrial city of Pittsburgh. Pennsylvania is the single biggest swing state prize under the US Electoral College system, which awards influence in line with population.

Both sides say they are encouraged by early turnout numbers, with over 78 million people having voted already, around half of the total number of ballots cast in 2020.

The closeness of the 2024 White House race reflects a deeply divided United States, as it chooses between two candidates whose visions could scarcely be more different.

Former president Trump has doubled down on his dark and violent rhetoric in his pursuit of a second term which would make him the first convicted felon and, at 78, the oldest major party candidate ever elected.

Vice President Harris, 60, has meanwhile made an astonishing rise to the top of the Democratic ticket after President Joe Biden dropped out of the race in July.

Harris is hoping abortion is a key issue that can hurt Trump, especially with woman voters, while Trump has focused on migrants and the economy and dubbed political opponents the “enemy from within.”

They have both embarked on a zig-zag through the swing states, with raucous rallies, podcast interviews to reach reluctant voters, and stunts such as Trump riding in a trash truck and Harris appearing on television comedy show “Saturday Night Live.”

On the campaign trail Sunday, Trump mused to supporters that he wouldn’t mind if journalists were shot, raised baseless allegations of election fraud and dwelt in gory detail on crimes by undocumented immigrants.

“Kamala -- you’re fired, get out,” Trump told a cheering crowd in Georgia.

Trump added he “shouldn’t have left” the White House after he lost his 2020 reelection bid to Biden, and then tried to overturn the results, culminating in the January 6, 2021 assault on the US Capitol.

Fears are mounting that he will again refuse to accept the result if defeated, and there is also concern that election workers could come under threat in the tense days ahead. Some election staff have been given panic buttons to quickly alert authorities in emergencies, while at least two states, Nevada and Washington, have activated the National Guard in case of unrest.

For Harris’s part, after some more encouraging recent polls, she told a noisy rally in Michigan on Sunday that “we have momentum -- it’s on our side.” Harris also courted the large Arab-American community in Michigan that has denounced US handling of the Israel-Hamas war, saying she would do “everything in my power to end the war in Gaza.”

The final days of the campaign have seen both candidates roll out high-profile surrogates. Trump-supporting tech tycoon Elon Musk has been making $1 million giveaways to registered voters, while Harris has called on the star power of former president Barack Obama and ex-first lady Michelle Obama and singer Beyonce.

But outgoing President Biden, 81, has been notably absent from the trail since a gaffe in which he referred to Trump’s supporters as “garbage” last week.

Biden will spend most of the last day of the campaign at the White House, while Harris will start her day with an event in his hometown of Scranton, Pennsylvania.