When Sen. Elizabeth Warren first debated with former Vice President Joe Biden in 2005, she was a professor at Harvard, and he was a senator from Delaware. The issue at hand was a bill that would make it more difficult for consumers to file for bankruptcy. Biden advocated for the bill, arguing that allowing consumers to file for bankruptcy would be unfair to creditors. Warren argued that her research showed bankruptcy was more likely to occur due to unfortunate circumstances rather than reckless behavior. When she became a senator in 2013, Biden told her at her swearing in that she “gave [him] hell” during the hearing.

On Thursday, the two will again go head-to-head, sharing the stage for the first time since they both launched their bids for the president. In the last 19 years, Warren has engendered herself to the party’s left-leaning base while Biden has steadfastly remained moderate.

“They have just these completely opposite worldviews. They very neatly represent two polar opposites of the Democratic Party,” Washington Post Reporter Annie Linskey said on Boston Public Radio Tuesday. “Joe Biden has come up in the party as a guy who knows how to get things done, to reach across the aisle [and] to build coalitions. ... Elizabeth Warren has come up through politics through a less traditional route. She came from the world of academia and a more activist perspective.”

Though Biden began the race as the clear front-runner, his lead has shrunk while Warren's popularity has been on the rise.

Linksey said she thinks while many viewers Thursday night will be looking for a fight, Warren will avoid engaging in a direct debate with Biden, using the stage instead as an opportunity to improve her name recognition among voters.

“She’s really telegraphing ... that [she] sees these debates as a continued opportunity to introduce herself to Americans,” Linskey said. “She’s not as well-known as the former vice president or even Bernie Sanders, for that matter, so she does not have a strong incentive to take a whack at either of those people.”

The Democratic debate will be held in Houston on Thursday, Sept. 12.