Former Vice President Joe Biden and Sen. Kamala Harris of California will square off for a second time in the upcoming Democratic debates in Detroit after capturing much of the attention in last month's debates for their clash over race.

Biden, who continues to lead public polling, and Harris will likely dominate much of the debate on July 31. Harris, who has seen her poll numbers rise since the June debates, criticized Biden's record on busing as a remedy to desegregate schools in the 1970s. Biden has adamantly defended his civil rights record, arguing that he never opposed voluntary busing.

The crowded race for the Democratic nomination has so far featured little swiping, with most candidates focused on attacking President Donald Trump. The June debates showcased the first real clash between two prominent Democrats in what may be a protracted fight among more than 20 candidates for the Democratic nomination.

Biden acknowledged after the debate that he was caught off guard by the attack from Harris. The upcoming debate gives him a chance to come out harder on his Democratic opponents and defend his long voting record that has come under intense scrutiny since entering the race. But Biden has mainly kept the focus on Trump, a strategy that shows the front-runner is setting his sights on the general election.

Biden could also take heat at Wednesday's debate from Sen. Cory Booker of New Jersey, who has publicly challenged the former vice president's civil rights record. Booker spoke out after Biden name-checked two segregationist senators as a way to show he was able to work with political opponents during his decades as a senator. Booker called on Biden to apologize, but Biden pushed backed: "Apologize for what? Cory should apologize."

Meanwhile, Harris could also face some questioning from debate moderators about her exact position on single-payer health care. When asked at the June debate if the candidates support ending private health insurance for government-run health care, only Harris and Sanders raised their hands.

But following the debate, she said that she misheard the question and thought the moderator asked if she'd personally be willing to give up private insurance. Harris clarified that she supports Medicare for All "and under Medicare for All policy, private insurance would certainly exist for supplemental coverage."

The Democratic debates in Detroit will again be held over two days, with 10 candidates on stage each night. CNN held a live drawing Thursday night to randomly determine the lineups for the July 30 and 31 debates. Democrats have been holding debates in states that are critical to winning the White House. Trump pulled off a close victory in Michigan, becoming the first Republican to win the state since 1988.

The other two front-running candidates, Sens. Elizabeth Warren of Massachusetts and Bernie Sanders of Vermont, will debate on Tuesday, July 30. With little daylight between the candidates' messages of combating government corruption and elevating the middle class, the debate will give each a chance to distinguish themselves.

Warren, who has debuted a new plan nearly every week, has also seen a bounce in polling. She also ranked in the top three in second-quarter fundraising despite her ban on high-dollar fundraisers. She came in third with $19.1 million raised, coming in just above Sanders' haul of $18 million.

Warren and Sanders will be joined on stage by a number of moderate Democrats, who will likely attack the two progressives for some of their top priorities, including Medicare for All and free tuition at public colleges and universities.

On July 30, the lineup includes Warren, Sanders, South Bend, Indiana, Mayor Pete Buttigieg, former Rep. John Delaney of Maryland, former Gov. Hickenlooper of Colorado, Rep. Tim Ryan of Ohio, Gov. Steve Bullock of Montana, author Marianne Williamson, Sen. Amy Klobuchar of Minnesota, and former Rep. Beto O'Rourke of Texas.

The lineup for July 31 includes Harris, Biden, Booker, former Housing and Urban Development Secretary Julian Castro, Sen. Kirsten Gillibrand of New York, Rep. Tulsi Gabbard of Hawaii, Sen. Michael Bennet of Colorado, New York City Mayor Bill de Blasio, Gov. Jay Inslee of Washington, and businessman Andrew Yang.

