Titled "An Urgent Conversation with the American People," the multi-hour, livestreamed discussion came ahead of Congress' return to session on Monday.
Protesters were demanding New York Mayor Bill de Blasio fire the police officer accused of using a fatal chokehold on Eric Garner.
Ten candidates, including Elizabeth Warren, Cory Booker, Julian Castro and Beto O'Rourke, converged on stage in Miami Wednesday for the first Democratic candidate debate.
Democratic presidential candidate Joe Biden is dismissing calls to apologize for saying that the Senate "got things done" with "civility" even when the body included segregationists with whom he disagreed.
Democratic candidates for president will have to prove themselves in polls and donations to participate in the debate on ABC this September.
Before he was elected to the Senate, Cory Booker served on Newark's city council and as the city's mayor.