Biden, Harris set for second Democratic debate showdown

Former Vice President Joe BidenJoe BidenDemocrats worry they don't have right candidate to beat Trump Trump threatening to fire Mulvaney: report Giuliani pens op-ed slamming 'unprecedented' impeachment inquiry MORE will face off against Sen. Kamala HarrisKamala Devi HarrisOutsider candidates outpoll insider candidates Poll: Buttigieg leads Democratic field in Iowa Press: Another billionaire need not apply MORE (D-Calif.) for a second time on the second night of the CNN Democratic debates in Detroit on July 31.

Meanwhile, Sen. Bernie SandersBernie SandersDemocrats worry they don't have right candidate to beat Trump Overnight Health Care: Top health official defends contract payments to Trump allies | Vaping advocates confident Trump will turn from flavor ban | Sanders gets endorsement from nurses union Krystal Ball credits Gabbard's upswing in 2020 race to 'feckless' Democratic establishment MORE (I-Vt.) will take on Sen. Elizabeth WarrenElizabeth Ann WarrenDemocrats worry they don't have right candidate to beat Trump Overnight Energy: BLM staff face choice of relocation or resignation as agency moves | Trump says he's 'very much into climate' | EPA rule would expand limits on scientific studies Krystal Ball credits Gabbard's upswing in 2020 race to 'feckless' Democratic establishment MORE (D-Mass.) on the first night of the forum, July 30. 

Sen. Cory BookerCory Anthony BookerOutsider candidates outpoll insider candidates The Hill's Campaign Report: Bloomberg looks to upend Democratic race Poll: Biden support hits record low of 26 percent MORE (D-N.J.) also will take the stage on July 31, along with former Housing and Urban Development Secretary Julián Castro, tech entrepreneur Andrew YangAndrew YangOutsider candidates outpoll insider candidates Is Andrew Yang's pivot working? New Quinnipiac poll finds Biden leading in New Hampshire MORE, Sens. Michael BennetMichael Farrand BennetPress: Another billionaire need not apply Democrats debate how to defeat Trump: fight or heal Overnight Energy: EPA watchdog slams agency chief after deputy fails to cooperate in probe | Justices wrestle with reach of Clean Water Act | Bipartisan Senate climate caucus grows MORE (D-Colo.) and Kirsten GillibrandKirsten GillibrandSenate panel clears controversial Trump court pick Advocates step up efforts for horse racing reform bill after more deaths Harris proposes keeping schools open for 10 hours a day MORE (D-N.Y.), Washington Gov. Jay InsleeJay Robert InsleeO'Rourke ends presidential bid Sunrise Movement organizer: Sanders, Warren boast strongest climate change plans Overnight Energy: Farmers say EPA reneged on ethanol deal | EPA scrubs senators' quotes from controversial ethanol announcement | Perry unsure if he'll comply with subpoena | John Kerry criticizes lack of climate talk at debate MORE (D), New York Mayor Bill de BlasioBill de BlasioDe Blasio slams Bloomberg run for president: He 'epitomizes the status quo' The Hill's 12:30 Report: Washington braces for public impeachment hearings Trump NYC Veterans Day speech met with protests MORE (D), and Rep. Tulsi GabbardTulsi GabbardOutsider candidates outpoll insider candidates Krystal Ball: Tulsi Gabbard surges, is she the most electable? New Quinnipiac poll finds Biden leading in New Hampshire MORE (D-Hawaii). 

South Bend, Ind., Mayor Pete ButtigiegPeter (Pete) Paul ButtigiegDemocrats worry they don't have right candidate to beat Trump Saagar Enjeti rips Buttigieg for praising Obama after misquote Krystal Ball credits Gabbard's upswing in 2020 race to 'feckless' Democratic establishment MORE (D) will join Sen. Amy KlobucharAmy Jean KlobucharGoogle sparks new privacy fears over health care data Krystal Ball credits Gabbard's upswing in 2020 race to 'feckless' Democratic establishment Outsider candidates outpoll insider candidates MORE (D-Minn.) and former Rep. Beto O'RourkeBeto O'RourkeO'Rourke says he 'absolutely' plans to stay in politics Krystal Ball: Buttigieg is 'the boomer candidate' Language is a weapon in political warfare — if the media play along MORE (D-Texas) on July 30, along with Rep. Tim RyanTimothy (Tim) RyanStrategists say Warren 'Medicare for All' plan could appeal to centrists Trump mocks O'Rourke after Democrat drops out of race The Memo: What the leading 2020 Dems need to do MORE (D-Ohio), Montana Gov. Steve BullockSteve BullockPress: Another billionaire need not apply Obama's former chief economist advising Buttigieg The Hill's 12:30 Report: Trump says Dems shouldn't hold public hearings MORE (D), former Colorado Gov. John HickenlooperJohn HickenlooperKrystal Ball dismisses Rahm Emanuel's 'Medicare for All' criticism as a 'corporatist mantra' Trump says remark about Colorado border wall was made 'kiddingly' Colorado governor mocks Trump for saying he's building wall there MORE (D), former Rep. John DelaneyJohn Kevin DelaneyBloomberg run should push Warren to the center — but won't The Hill's 12:30 Report: Impeachment fight enters new stage Biden hits Warren over 'Medicare for All' plan MORE (D-Md.) and author Marianne WilliamsonMarianne WilliamsonYang seeks donations for 2020 rival Marianne Williamson: 'She has much more to say' Pushing results, not polarization, in New Hampshire Williamson focuses on reparations in first ad of presidential campaign MORE

The candidates with the highest poll numbers will be center stage at the debates. 

Warren and Sanders will be center stage the first night, while Harris and Biden will stand next to each other on the second night. 

The assignment is a rematch for Biden and Harris. The California senator attacked Biden head-on during the first debate, criticizing his civil rights record, specifically on busing. 

Harris experienced a bump in the polls and fundraising after she confronted Biden in the forum. 

Biden said after the first debate that he did not expect Harris to confront him in the way that she did on the issue. 

Booker, who has criticized Biden's past comments on working with segregationist senators, will stand on the other side of Biden, which could result in more moments of friction. 

The debate will also mark the first time progressives Sanders and Warren go head to head. 

Warren has risen in the polls in recent months, laying out detailed plans on her progressive policies. 

Sanders, who shares similarities with Warren on progressive policies, has in turn plateaued or dipped in polls. 

The two senators will likely seek to differentiate their policies and tout their own.