Sanders’s ascendancy in the nomination fight places the Democratic Party in a double bind. Not only is he potentially a dangerously weak general election candidate but, if an Anybody-But-Bernie movement materializes and successfully defeats him at the convention, Sanders supporters — more than backers of any other major candidates — are likely to bolt on Election Day and vote for either a third-party candidate or even Trump (as many Sanders supporters did in 2016), or sit out the contest altogether. In 2016, more than 7 million votes were cast for third-party candidates, more than enough to have given the election to Hillary Clinton.

A January 22-23 Emerson College survey asked Democratic primary voters “will you vote for the Democratic nominee even if it is not your candidate?” 87 percent of Joe Biden supporters said yes, as did 90 percent of those backing Elizabeth Warren and 86 percent of those aligned with Pete Buttigieg. 53 percent of Sanders supporters said yes, 16 percent said no, and 31 percent said they were undecided.