WASHINGTON — Former Vice President Joe Biden will be flanked by two progressive rivals at the next Democratic debate as the 10 leading candidates appear on stage together for the first time.

The 2020 front-runner will be center stage at the Sept. 12 event in Houston, according to sponsor ABC News, and face Vermont Sen. Bernie Sanders on his right and Massachusetts Sen. Elizabeth Warren on his left.

The staging largely reflects the candidates' standing in polls, with the strongest candidates closest to the middle.

.@ABC announces podium order for qualifying candidates at third Democratic Debate on September 12: https://t.co/4UMjNSaOk2 pic.twitter.com/mzPME3SPKH — ABCNews PR (@ABCNewsPR) August 29, 2019

It will be the first time Warren and Biden will appear in a debate together, since they were split across different nights in June and July's two-night stands.

Warren and Sanders joined forces in the last debate to fend off attacks from more moderate rivals and they could tag-team Biden — or potentially seek to differentiate themselves from each other.

Also near to Biden will be California Sen. Kamala Harris, with whom he has clashed on race, and Mayor Pete Buttigieg of South Bend, Indiana, who, at 37, has made a more subtle generational critique of Biden, who is 76.

Toward the wings of the stage will be New Jersey Sen. Cory Booker, entrepreneur Andrew Yang, former Texas Rep. Beto O'Rourke, former Housing Secretary Julián Castro, and Minnesota Sen. Amy Klobuchar.