The demographic patterns in these races are clear. African-American candidates were able to build an energized Democratic coalition of black voters, white liberals and younger voters to swamp more-established candidates in primaries. But white liberal candidates struggled to expand their support beyond the most predictable precincts, unable to build racially-diverse coalitions for their progressive messages.

Consider: Nixon’s weakest showing in the primary occured in the Bronx, where she won a measly 17 percent of the vote in the predominantly black and Hispanic New York city borough. Despite facing criticism for making patronizing comments about African-American leaders in Illinois, black voters provided Pritzker with critical support against more-progressive opponents. Perriello struggled badly in majority-black cities and counties across Virginia, dooming his chances against Northam.

It’s a reminder that the Democratic party’s crucial bloc of black voters is more interested in electing familiar faces than supporting true-blue ideologues. When African-American candidates can excite white progressives, it’s a potent combination in a Democratic primary. White progressives, dependent on ideological fervor alone, often underachieve in party primaries where nearly half of voters still identify as moderate or conservative.