There were originally a record-breaking six women vying for the Democratic nomination to take on Republican President Donald Trump in November
Democratic presidential contender Joe Biden, who had hinted he might choose a woman as his vice presidential running mate if he is picked as the party's nominee, committed to doing so during his debate with rival Bernie Sanders on Sunday.
"If I'm elected president, my Cabinet, my administration, will look like the country, and I commit that I will in fact appoint and pick a woman as vice president. There are a number of women who are qualified to be president tomorrow. I would pick a woman as my vice president," Biden said.
There were originally a record-breaking six women vying for the Democratic nomination to take on Republican President Donald Trump in November - US Senators Elizabeth Warren, Amy Klobuchar, Kamala Harris and Kirsten Gillibrand, along with US Representative Tulsi Gabbard and Marianne Williamson.
Only Gabbard remains in the race, although she is polling below 5% nationally and was not eligible to participate in the debate.
Sanders said that "in all likelihood," he would choose a woman as his running mate, but did not make as firm a commitment.
"In all likelihood, I will. 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 tendency is to move in that direction," Sanders said.
Two women were previously nominated by the major parties for US vice president - Democrat Geraldine Ferraro in 1984 and Republican Sarah Palin in 2008. Both their tickets were defeated. Democrat Hillary Clinton, the first woman nominated for president by a major party, lost to Trump in 2016.