Transcript for Sanders, Warren the focus of Dem debate as other candidates try to appeal to voters
And tonight, that issue of race and this rhetoric lately will likely come up during this newest democratic presidential debate. Another likely topic, front-runner Joe Biden. He won't be on the stage tonight in night one. A new national poll showing the former vice president increasing his lead, with 34% of democratic voters now supporting him. Elizabeth Warren, kamala Harris, Bernie Sanders all trailing behind. Let's get right to Mary Bruce, she's live for the debate tonight. This is a make or break moment, really, for many of the candidates. They have to try to break through the pack, and it's a large one. Reporter: Well, David, for so many of the candidates on the wings here tonight who have been struggling to break through, they have to have some kind of moment here if they want to survive. As for the candidates in that middle tier, like Amy klobuchar, Beto O'rourke and Pete buttigieg, they are looking for a much-needled boost. The moderate candidates are trying to distinguish themselves on issues like health Carol and education. They are also trying to make the case they can appeal to voters in the key swing states. David? Right at the center tonight, Bernie Sanders and Elizabeth they have off teamed up in the but of course, the big question tonight, will they take each other on? Reporter: The focus is all on these two Progressive powerhouses. Elizabeth Warren and Bernie Sanders. They are fighting for the same voters and they are close friends and political allies. Tonight is going to test their truce, but both campaigns tell us this is simply not the night to start going after each other. David? Mary Bruce with us live tonight from Detroit. Mary, thank you.
This transcript has been automatically generated and may not be 100% accurate.