The marquee races are taking place in swing states like Arizona, Georgia, Nevada, Pennsylvania and Wisconsin, all of which could help determine the outcome of the 2024 presidential contest.

While the rejections may have some basis in state law, experts say they appear to go against a principle, enshrined in federal law, of not disenfranchising voters for minor errors.

Both President Biden and his predecessor, Donald Trump, are hoping to provide their parties late boosts on the last full day of campaigning before midterm elections that could reshape the balance of power in Washington.