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Potential Democratic voters will get to see current top-polling Democratic candidates Joe Biden and Bernie Sanders go against each other Thursday night during the second debate. But what about Elizabeth Warren, who’s solidified her hold among the top three candidates and is pushing Sanders? Because of the large number of candidates and the two-night format, some of the best potential face-offs aren’t happening.

Here are a few of the candidates who would likely benefit from debating on the same night and what Americans will be missing:

Bernie Sanders vs. Elizabeth Warren

Elizabeth Warren has been cutting into and even surpassing Bernie Sanders’ second place position in the polls. According to data aggregated by Real Clear Politics, Warren is about three points behind Sanders, but she leads him in the most recent Monmouth poll. With their progressive messages, it’s likely one of them will eventually need to pull voters away from the other to challenge frontrunner Biden.

Both Sanders and Warren support policies like free college tuition, the elimination or downsizing of student debt, the breakup of Big Tech, an increase of taxes on the megarich and a Green New Deal. On stage they would be able to discuss the different nuances of each of their plans (Sanders, for instance, wants to eliminate all student debt; Warren would cancel up to $50,000 of debt for households making less than $100,000 and cancel no debt of households making $250,000 or more) and better showcase the major difference that underscores their similar views: Sanders is an avowed socialist who speaks openly of a political revolution. Warren is a capitalist who wants to increase regulation.

If Warren and Sanders were together, they might also be able to pull the other candidates further left in live time. Instead, progressives will have to settle for hearing their messages on separate nights.

Cory Booker vs. Joe Biden

Until last week, a debate between Booker and Biden had little appeal. Then Biden remarked that he had worked across the aisle with well-known segregationists James Eastland and Herman Talmadge. “I was in a caucus with James O. Eastland,” he said. “He never called me ‘boy.’ He always called me ‘son.’” Booker responded by saying it was wrong to use those relationships as an example for unity. Biden said Booker should apologize for questioning his commitment to civil rights. Biden has since said his original comments were taken out of context.

Booker continued to disparage Biden Sunday on “This Week With George Stephanopoulos.” “I listened to the full totality of what he was talking about and frankly I heard from many, many African Americans who found the comments hurtful,” Booker said on the show. “Look, we make mistakes, we sometimes tread on issues that maybe we aren’t knowledgeable of.”

Unfortunately for Booker, who has barely registered as a candidate despite years in the public eye, he won’t be able to emphasize his message to Biden’s face. Sen. Kamala Harris, who also criticized Biden’s remarks, will be debating Biden on the second night.

Beto O’Rourke vs. Pete Buttigieg

Last November, Beto O’Rourke was the shiny young future of the Democratic party. He had gone from unknown Congressman to a hyped, but ultimately unsuccessful, challenger to Sen. Ted Cruz. While raising some $80 million, O’Rourke garnered attention from the likes of Beyonce and LeBron James, setting the path for his presidential run.

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Then Pete Buttigieg arrived on the scene. The South Bend Mayor is younger and speaks more Norwegian. They both have charisma and can rhapsodize on numerous subjects, albeit without staking many clear positions so far.

And Buttigieg has outdone O’Rourke. His background as a veteran, the potential history-making accomplishment of being the first gay man elected president and his message to the Christian Left have let him stand out from O’Rourke. O’Rourke’s first major policy paper was on climate change, a topic owned by candidate Jay Inslee, and he has not gained significant momentum with any policy rollouts since. In the aggregated Real Clear Politics data, Buttigieg is at 7.1%, in fourth place among the candidates, and O’Rourke is at 3.6%, in sixth place.

On the same debate stage, O’Rourke might have an opportunity to take back from Buttigieg his place as the charismatic candidate adept at wowing crowds. But he’ll have to wait longer.

Bill de Blasio vs. Kirsten Gillibrand

With New York-centric leadership roles, New York City mayor Bill de Blasio and Sen. Kirsten Gillibrand should potentially have connections to many of the same donors and a massive, blue voting base. One of them will need to stand out as a better choice and receive the funding necessary to survive further into primary season (neither is polling above 1%), and this debate will not offer Gillibrand or de Blasio the opportunity to directly gain momentum against the other.

There’s another unfriendly reality for both candidates: In many cases, the wealthiest New Yorkers are favoring Biden, Buttigieg and Kamala Harris.

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