They will have a little more time to answer questions than in the earlier debates - one minute and 15 seconds for direct responses to questions and 45 seconds for rebuttals. Candidates will have the opportunity to deliver opening statements, but there will be no closing statements.
The three-hour debate will air live on ABC and Univision and their streaming platforms.
Biden, likewise, doesn't often mention Warren or Sanders.
The previous debates, in June and July, featured a dizzying 20 hopefuls over two long nights, with seven months to go before the first votes are cast in Iowa to pick the nominee.
This poll marks one of the only times that Biden has been in jeopardy of losing his front-runner status.
Progressive Democrats Elizabeth Warren and Bernie Sanders will share the debate stage for the first time with establishment favorite Joe Biden Thursday night in a prime-time showdown displaying sharply opposing notions of electability in the party's presidential nomination fight.
Sanders, at 78 the oldest candidate in the field, is narrowly leading Warren at 17.3 percent support, and has largely avoided clashing with his Senate friend and fellow progressive. That will create an interesting dynamic, as the frontrunner will be in between the two major candidates who have eschewed big-dollar fundraising and who want to push the party much further to the left on economic issues. For example, Joe Biden's camp wondered if the media is in the tank, so to speak, for a specific candidate not named Biden (or Harris).
As Vox notes, every candidate who qualified for tonight's debate is automatically qualified for the October debate as well.
And although about one-fifth the roughly 20,000 Minnesotans who gave to Klobuchar also gave to other candidates, the other 80 percent gave exclusively to her campaign, suggesting a hometown advantage not all candidates enjoy.
Shows Klobuchar small donors by state, shaded less to more. Her candidacy barely made the cut and she'll need to work hard to capture attention away from the front runners to have a meaningful impact. Candidates have to reach the same criteria as Thursday's debate to qualify, but the field is already looking bigger.
This debate is set in the home state of two candidates: former Texas Rep. Beto O'Rourke and former Housing and Urban Development Secretary Julian Castro.