During Tuesday's Democratic presidential debate, Vermont senator Bernie Sanders and Massachusetts senator Elizabeth Warren were each asked about a conversation they had just over a year ago. When they discussed the presidency, Sanders reportedly said that a woman could not be elected president of the United States.

He's repeatedly denied ever saying such a thing -- what he did say, he claims, is that President Donald Trump would "weaponize whatever he could," including an opponent's race or gender, in order to win. Meanwhile, four people who heard about the conversation right after it happened, and Warren herself once the story came out, confirmed that, yes, Sanders did say that. 

Sanders and Warren, who are longtime friends and both hold progressive views, have been abiding by an informal agreement not to attack each other in the press or on the campaign trail. That agreement mostly held during last night's debate, despite the fact that the Iowa caucuses are less than three weeks away. So when CNN's Abby Phillip asked Sanders about the incident, he once again denied it but added that he didn't want to waste much time discussing it "because this is what Donald Trump and maybe some of the media want." 

As for Warren, when Phillip asked her how she felt when Sanders made the comment, Warren said, "I disagreed." But then she went right for the heart of the matter, which is that a lot of people seem to agree with the comment Sanders says he never made. An Ipsos poll of 1,005 Americans, weighted to reflect the overall population, found that 39 percent believe it's true that "A woman would have a harder time than a man running against Donald Trump in 2020." And while 74 percent said they'd be comfortable with a female president, only 33 percent thought their neighbors would be. 

People who think a woman can't be elected? They are very wrong. Whatever Sanders may have said in 2018, here's what he said on the debate stage: "Hillary Clinton won the popular vote by three million votes. How could anyone in a million years think that a woman could not be elected president of the United States?"

If that's not enough to convince you, consider the 2018 midterm elections, in which more female candidates won office than ever before for the simple reason that there were more women running for office than ever before. The data shows that when women and men run for office in equal numbers, they win in equal numbers.

Only the women were undefeated

Warren made this point in a different way during the debate by pointing out that the four men on the stage (presidential candidates Joe Biden, Pete Buttigieg, Tom Steyer, and Sanders) had lost 10 elections among them, whereas the two women on the stage, Warren and Amy Klobuchar, had won every election they'd been in. Warren added that she was the first Democratic candidate in 30 years to beat an incumbent Republican. (This led to a bit of mathematical back-and-forth with Sanders, who noted that he'd beaten a Republican incumbent in 1990 -- which, of course, is just barely 30 years ago.)

All right, you might say, maybe women can win smaller elections and become senators or governors, but they can't be elected leader of the nation. Except that women have been elected to lead many, many other countries, including Canada and the United Kingdom, Germany, Ireland, and Iceland. Some of these nations may have less entrenched gender bias than the U.S., but consider the Philippines, a nation where gender bias remains very strong but which has had two female presidents. In Pakistan, women are not allowed to show even an inch of leg, and many of them wear burqas or headscarves. Nevertheless, Pakistanis have elected Benazir Bhutto as prime minister not once but twice. Or just think back to before 2007, when many polls indicated that the American public would never elect a black president.

Polls suggest that if the election were held tomorrow, Biden and Sanders would stand a good chance of beating Trump -- but so would Warren, although by a smaller margin. It reminds me of a lot of jobs that women supposedly couldn't do: preacher, astronaut, football player, combat soldier, NBA coach, secretary of state. Most thought women could never get jobs like these, let alone be any good at them. But then they did. And they are.

Correction: An earlier version of this article misspelled the last name of CNN's Abby Phillip.