Vermont Sen. Bernie Sanders, the challenger with the most momentum, represents a state that’s 95 percent white, where Asian-Americans and multi-racial voters outnumber blacks. He’s focused most of his campaign message on income inequality, constraining Wall Street excess, and campaign finance reform, while avoiding discussions on race relations, urban policing, or gun control. Only 25 percent of non-white Democratic voters said they’d even consider backing the senator’s presidential bid, according to last month’s NBC/Wall Street Journal survey.

Former Maryland Gov. Martin O’Malley, despite representing a state where nearly half of Democratic voters are black, has been unable to make inroads with his onetime political base. In fact, he drew some jeers when he returned to Baltimore in the wake of violent rioting that tore apart the city. As mayor, his tough-on-crime measures were popular with Maryland voters, but the no-tolerance approach alienated many African-American voters in the state’s largest city. Even some of his base-pleasing accomplishments as governor—such as his early support for gay marriage—hold limited appeal with black voters. In a recent speech, he awkwardly compared his experience as a “minority white candidate” for mayor to the broader African-American experience.

Meanwhile, Clinton’s other rival is more conservative than the entire Republican presidential field when it comes to the Confederate flag.