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WATCH: Candidates face off in second night of 2020 Democratic debate

Ten 2020 Democratic presidential candidates faced off Thursday in the second night of debates hosted by NBC News.

The second night of the first 2019 Democratic presidential debate was held Thursday. Watch in the video player above.

Democratic divisions over race, age and ideology surged into public view during the debate, including a prime-time clash punctuated by a heated exchange between former Vice President Joe Biden and California Sen. Kamala Harris.

It was one of several moments that left the 76-year-old Biden, who entered the night as his party’s fragile front-runner, on the defensive as he worked to convince voters across America that he’s still in touch with the Democratic Party of 2020 — and best-positioned to deny President Donald Trump a second term.

“I do not believe you are a racist,” Harris said to Biden, though she described his record of working with Democratic segregationist senators on non-race issues as “hurtful.”

Biden called Harris’ criticism “a complete mischaracterization of my record.” He declared, “I ran because of civil rights” and later accused the Trump administration of embracing racism.

READ MORE: 5 takeaways from the first 2020 Democratic debate

The debate marked an abrupt turning point in a Democratic primary in which candidates have largely tiptoed around each other, focusing instead on their shared desire to beat Trump. But the debate revealed just how deep the fissures are within the Democratic Party eight months before primary voting begins.

Who was there: Twenty-four candidates are currently in the race for the Democratic nomination, but only 20 qualified for the debates by meeting the Democratic National Committee’s criteria of either receiving financial support from at least 65,000 unique donors or polling at least 1 percent in three DNC-approved national or statewide polls.

The candidates were divided into two groups of 10; groupings were drawn at random, and the candidates are positioned so that those with the highest polling numbers are in the middle of the stage).

The lineup for Thursday night, in the order they appeared on stage: Marianne Williamson, John Hickenlooper, Andrew Yang, Pete Buttigieg, Joe Biden, Bernie Sanders, Kamala Harris, Kirsten Gillibrand, Michael Bennet and Eric Swalwell.

Who wasn’t there? The following four candidates failed to qualify: Steve Bullock, Seth Moulton, D-Mass., Wayne Messam, and Joe Sestak, who joined the race this past weekend.

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Bullock planned a counter-program the debates by participating in two locally televised town halls in the key early voting states of New Hampshire and Iowa.

Moulton was slated to be in Miami, making the rounds on cable news and attending a Florida Democratic Party reception.

Looking ahead: The criteria to qualify for the second round of debates, which will be hosted by CNN in Detroit on July 30 and 31, remain the same as the criteria for the ones this week.

The third series of debates, which will be hosted by ABC News on Sept. 12 and 13 (location to be determined), has stricter qualification guidelines. Candidates must receive 2 percent support in four approved national or early state polls and 130,000 unique donors from at least 20 states.

The Associated Press contributed to this report.