Explainer: Why we may not know the winner of the US presidential election on November 5

Republican presidential nominee former President Donald Trump, left, speaking at a campaign event Sept. 25, 2024, in Mint Hill, N.C., and Democratic presidential nominee Vice President Kamala Harris, right, speaking a campaign event October 19, 2024, in Atlanta.

The US presidential election will take place on November 5, but the winner of the razor-thin race between Democrat Kamala Harris and Republican Donald Trump may not be known for days after the polls close.

As ballots are counted, one candidate may appear to be leading based on early returns, only for a rival to close the gap as more votes are tallied.