The drama to come out of Tuesday’s Democratic presidential debate — the last one before the Iowa caucuses next month — had nothing to do with policy differences or competing visions for the future of the party. It revolved around an aborted handshake, charges of sexism and a dispute over who said what at a dinner in 2018 between the two New England senators now fighting to be the field’s progressive standard-bearer, Elizabeth Warren and Bernie Sanders.

Ms. Warren contends that, during a tête-à-tête in late 2018, Mr. Sanders told her he did not believe that a woman could win the presidency. Mr. Sanders has dismissed the charge as “ludicrous” and initially accused some on the Warren campaign staff of lying about it.

When asked about the comment by the debate moderators, Mr. Sanders doubled down on his denial. “Anybody knows me knows that it’s incomprehensible that I would think that a woman cannot be president of the United States.”

Now, one could point out that believing a woman can be president of the United States is not the same as questioning whether a woman can get elected president.