During the CNN/ Des Moines Register Democratic presidential debate, Sen. Bernie Sanders (D-VT) denied telling Sen. Elizabeth Warren (D-MA) during a private meeting in 2018 that he did not believe a woman could win the presidency.

source https://www.cnn.com/videos/politics/2020/01/15/sanders-warren-female-president-democratic-debate-des-moines-iowa-sot-vpx.cnn