Most of Biden’s rivals proved to have limited appeal beyond their base. Elizabeth Warren did well with educated white voters but poorly with everybody else. (In Massachusetts, she won in Somerville, the home of many Harvard graduate students, and in Arlington, the home of many Harvard faculty members, but few other localities.) Pete Buttigieg struggled to attract younger voters. Amy Klobuchar never broke through outside the Midwest. Even Bernie Sanders, Biden’s most formidable rival, primarily appeals to voters who are robustly progressive and has performed poorly among black voters.

Biden, by contrast, has real strengths in virtually every demographic group. He did especially well among older and more moderate voters (and that matters for his ability to win the Electoral College in November). But he also did well among a host of other groups: He crushed the competition among African Americans, had significant support among Latinos, and made real inroads among educated white voters. Tellingly, his appeal also crosses ideological boundaries: In a number of states, he won a plurality of voters who consider themselves very liberal.

In 2016, it turned out that the mighty ideological commanders of the Republican Party had no more troops left. Though a pro-market economic orthodoxy had long dominated the thinking of the party’s leaders, most of their voters had never quite bought into it. In this electoral cycle, Michael Bloomberg and Sanders—in different ways— staked their chances of success on the hypothesis that the long-standing ideological commitments of the Democratic Party were equally hollow: Many voters, they wagered, are secretly hungering for a markedly different style of politics than that represented by Obama.

Bloomberg’s gambit has unambiguously failed. The former mayor of New York believed there was a widespread demand for the ideological centrism that appeals to coastal American elites: center-right economic policies that favor business coupled with center-left cultural policies. Bloomberg made for a compelling candidate on paper; he’s a political outsider with a track record as the mayor of a big city and unlimited means of financing his campaign. But the constituency for his brand of politics simply doesn’t seem to exist.

Read: Bernie Sanders gets a rude awakening

Sanders’s approach has a bit more empirical evidence on its side and may yet prove to have staying power. The senator believes that there is strong demand for a form of democratic socialism that, going beyond the abuses of the current system, paints capitalism itself as the enemy. His righteous anger at the dominance of special interests, which he expresses more forcefully than any of his rivals, has won him a lot of fans. This has allowed Sanders to remain a competitor for the nomination.