In many of the coming primaries, including most of tomorrow's contests, independents will not be welcome at the polls. And Bernie Sanders supporters are not happy about that.
Last week, New York's closed primary and early deadline for registration came under fire from Bernie Sanders supporters who think that non-Democrats deserve a bigger say in who the Democrats nominate for president. Clinton won the primary, just as she has won every closed primary so far.
Sanders supporters will point out that closed primaries put them at a disadvantage, because their candidate is more popular with independents. And they are right. Very right.
Indeed, Sanders owes a lot of his delegates to the non-Democrats who have voted for him in open primaries. In exit polls, Sanders does well with the groups you have heard of. He does better with liberals, with young people, with white voters, with men. Hillary Clinton, on the other hand, does better with older voters, with nonwhite voters, with women.
But the divide between independents and self-identified Democrats is among the largest. Only Clinton's support among blacks is higher. In states where there are not enough black people to estimate their vote separately, like Massachusetts, Clinton still dominates among partisans.
This figure compares the candidates' differences in group support across the exit polls for the 22 states that CNN has reported on its website. This excludes all caucuses except Iowa and Nevada, so it doesn't represent Sanders's many recent wins in low-turnout caucuses. Consistent with her repeated victories, Clinton does better than Sanders on average for most groups, except for young people and self-identified independents. There is variation in each category. Those points on the far left are all Vermont, where Sanders crushed Clinton even among self-identified Democrats. Meanwhile, Clinton does well among even independents in many Southern states.
The pattern is very consistent with the expectations of The Party Decides, which argues that when party leaders coordinate on a favored candidate, that candidate wins. Yes, our book was obviously wrong about the party stopping Donald Trump, but so far, it's a good road map to the Democrats. In the book, we showed that the candidates who have more endorsements from party leaders do better among partisan voters, but not among independent voters. Partisan voters may take a cue from their leaders, but independents resist.
Of course, since most primary voters are party members, winning partisans is a good idea. In 2016, the primary electorate in even the most open state is still never less than majority Democratic, and on average about three-quarters of voters self-identify as Democrats. It is hard to win without them.
The story on Sanders has been one of race, of gender, of a new generation challenging the old, and all of that is true. But the simpler story may simply be that Sanders, until this cycle a non-Democrat himself, doesn't do so well with voters who identify as Democrats.