Tuesday’s primaries saw the final states cast presidential votes in the Democratic primary. More than 650,000 Democrats voted against Biden over the last four months by choosing options such as “uncommitted,” with others protesting in other states through write-ins, blank ballots, votes for other candidates and other means. Together, the hundreds of thousands of protest votes underscore the president’s political weakness with five months until Election Day. But they also provide a potential blueprint for a comeback.