Why was Mrs. Clinton so much more unpopular than Mr. Biden is now? There’s good reason to believe that gender plays a key role. For starters, Mrs. Clinton wasn’t just far less popular than Mr. Biden. She was far less popular than every male Democratic nominee since at least 1992. Neither Bill Clinton, Al Gore, John Kerry nor Barack Obama faced overwhelming public disapproval throughout their general election campaigns. Hillary Clinton did.

A major driver of the public’s extreme dislike of Mrs. Clinton was its perception of her as duplicitous. In a poll taken just days before the 2016 election, Americans deemed her even less truthful than Mr. Trump. By contrast, in a Pew Research Center poll late last month, Americans rated Mr. Biden as more honest than Mr. Trump by 12 points.

According to fact checkers, these public perceptions are wildly incorrect. PolitiFact, a project of the nonprofit Poynter Institute, rates the veracity of politicians’ assertions. According to its calculations, which are based on hundreds of individual statements, Mrs. Clinton isn’t only far more honest than Mr. Trump. She’s also more honest than Mr. Biden.