Former Vice President Joe Biden has pledged to pick a woman to be his running mate, should he get the Democratic nomination.
Biden also committed to picking the first black woman to serve on the US Supreme Court.
He made the pledge more than an hour into the first one-on-one debate with Senator Bernie Sanders, carried on CNN and Univision.
"My administration will look like the country and I commit that I will, in fact, appoint a woman to be vice president," Biden said. "There are a number of women qualified to be president tomorrow."
Sanders was asked if he, too, would pick a female running mate.
"In all likelihood, I will," Sanders said. "To me, it's not just nominating a woman. It is making sure that we have a progressive woman and there are progressive women out there. So my very strong tendencies is to move in that direction."
The debate was the first since Super Tuesday, and the first held in the midst of the coronavirus crisis. The candidates spent the first 40 minutes debating the response to the virus.
Biden sought to present himself as a forceful leader, saying that Americans should be assured that their virus treatments are covered and suggesting that the military should be called upon to assist in the response.
"I would call out the military now," he said. "This is like a war. In a war, you do whatever is needed to be done to take care of your people."
Sanders, meanwhile, argued that the virus had exposed the fundamental failure of the US health care system, and underscored the urgent need for Medicare for All.
"The dysfunctionality of the current health care system is obviously apparent," Sanders said. "Clearly we are not prepared, and Trump only exacerbates the crisis... One of the reasons we are unprepared and have been unprepared is that we don't have a system. We've got thousands of private insurance plans. That is not a system that is designed to provide health care to all people."
Biden, who opposes Medicare for All, countered that Italy's single-payer health care system has not protected that country from the crisis.
"It has nothing to do with Medicare for All. That would not solve the problem at all," Biden said. "It is not working in Italy right now and they have a single-payer system."
Sanders argued that the poor are likely to be hit hardest by the virus and the economic fallout.
"In this crisis we have got to start paying attention to the most vulnerable," he said. "Half of our people are living paycheck to paycheck."
The debate was held in CNN's studios in Washington, D.C., without a live audience. Biden and Sanders bumped elbows instead of shaking hands, , and stood at podiums spaced unusually far apart to model social distancing as part of virus control.