In an unprecedented move, former Vice President Joe Biden committed Sunday to choosing a female running mate should he receive the Democratic nomination.

No major candidate has ever pledged to pick a running mate based on demographics, nor narrowed the field of potential candidates so early on in the election.

Biden’s top competitor, Sen. Bernie Sanders (I-Vermont) did not fully commit to having a female running mate but said during the Democratic debate he would “in all likelihood” name a female running mate provided she shares his progressive views and “my very strong tendency [is] to move in that direction.”

Biden’s pledge to pick a woman as running mate was a response to a question posed by the debate moderators on how their cabinets will “ensure the best advice on issues that affect women’s physical and financial health.”

Biden replied that he intended to appoint a black woman to the Supreme Court saying, “It’s required that they have representation now, it’s long overdue.”

“If I am elected president, my cabinet — my administration — will look like the country,” he said. “And I commit that I will … pick a woman to be Vice President. There are a number of women who are qualified to be president tomorrow.”

The emphasis on cabinet demographics indicates that both men are recognizing the diversity of the Democratic Party and the need to build a diverse body of government in order to receive minority groups’ support.