Debate Night!

Tonight, former president Donald J. Trump and Vice President Kamala Harris will do their likely only presidential debate on ABC News. President Joe Biden suspended his reelection bid after he was forced out by party leaders after a disappointing debate performance in June.

The high stakes event expected to be viewed by millions of Americans and a key sliver of undecided voters.

Harris' momentum -- after her unusual rise as the Democrats' nominee shot her into a neck-and-neck race -- has now stalled, making the head-to-head matchup an opportunity to get that started again -- If she can adequately make the argument for her own candidacy and cast Trump as unfit for another term.

Trump, meanwhile, has struggled to find a way to consistently and effectively attack his new opponent but has remained highly competitive, thanks to a large base of immovable supporters and the broad swath of Americans who already have fixed views of him. Tuesday's debate offers him an opportunity to solidify his support while painting Harris in a negative light to an electorate that has less cemented perceptions of her.

Who's gonna win?

As it stands, it's a neck-and-neck race. Harris would like a moment that revives her momentum, which jolted her into contention but now is stalled; Trump would like a moment to erase some of the gains Harris has made and actually reverse her improved poll numbers.

In order to qualify for the September 10 ABC debate, presidential candidates need to meet the following criteria:

Be constitutionally eligible to hold the presidency

File with the Federal Election Commission

Appear on a sufficient number of ballots to have a mathematical possibility of winning a majority vote in the Electoral College

Agree to the rules of the debate

Have a level of support of at least 15% in four national public polls of registered or likely voters selected by ABC, with such polls dating between August 1 and September 3, 2024.

Harris and Trump were invited to the debate in early August.

Five polls met ABC's criteria for inclusion, with Harris and Trump meeting the 15% threshold in every poll.