Arlington, Virginia - The first early voters cast their ballots Friday for November's knife-edge presidential election, as Democratic candidate Kamala Harris headed for a campaign event focused on the hot-button issue of abortion.

Three US states – Virginia, Minnesota and South Dakota – were starting early voting, a practice that Republican nominee Donald Trump has previously cast doubt on when falsely claiming he won the 2020 election.

Dozens of people waited at an early voting polling station in the center of Arlington, Virginia, just outside Washington, AFP journalists saw.

A number had "Harris-Walz" shirts, while there were also some "Trump-Vance" signs in front of the building.

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"I'm excited," said Michelle Kilkenny (55), adding that voting early, "especially on day one, helps the campaign and raises the enthusiasm level."

Most states permit in-person voting or mail-in voting to allow people to deal with scheduling conflicts or an inability to cast their ballots on election day itself on November 5.

Former president Trump has frequently lashed out against anything except on-the-day voting, repeatedly blaming mail-in ballots for his 2020 defeat by Joe Biden – while also sometimes calling early voting into question, despite efforts by his campaign to promote it.

Trump (78) faces criminal charges for allegedly trying to overturn the 2020 result, after which his supporters assaulted the Capitol on January 6, 2021.

Every vote will count in a desperately close 2024 White House race, whose result Trump has once again refused to say he will accept.

Harris has erased Trump's lead since sensationally replacing President Biden as Democratic candidate in July, but remains neck-and-neck with the Republican.

The vice president is traveling on Friday to Atlanta, Georgia – one of the seven swing states expected to decide the election – to talk on the crucial issue of reproductive rights.

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Harris has heavily focused on the subject, believing Trump to be vulnerable due to his frequent boasting that his Supreme Court picks paved the way for the 2022 overturning of the national right to abortion.

At least 20 states, including Georgia, have since brought in full or partial abortion bans as a result.

Her campaign said she would "speak about the dangerous consequences of Trump abortion bans."

She would also focus on the deaths of two women in Georgia from delayed medical care caused by its restrictive measures, which were reported by ProPublica.

Harris met the family of one of the women, Amber Nicole Thurman, during a glitzy campaign event hosted by talk show star Oprah Winfrey on Thursday.

The star-studded event in Michigan, another battleground state, featured a number of Hollywood supporters, including actors Jennifer Lopez, Meryl Streep, and Julia Roberts.

Trump – who was due to attend a fundraiser in Miami on Friday – took a darker tone at an antisemitism event in the capital on Thursday.

"If I don't win this election... in my opinion, the Jewish people would have a lot to do with a loss," Trump said, repeating his grievance that Jewish voters have historically leaned towards the Democrats.

Republicans face trouble in another battleground state, North Carolina after the party's candidate for governor rebuffed calls to drop out following a report that he called himself a "Black Nazi" on a porn website.

With the end of his term approaching in January, Biden meanwhile continued his long goodbye.

The 81-year-old president was hosting a meeting at the White House on Friday to "direct his cabinet to sprint to the finish," an official said.

He will later start greeting the leaders of Australia, India, and Japan – the so-called Quad – at his home in Wilmington, Delaware, in a farewell to the alliance he has promoted as a counterweight to China.