Without question, the black community will, by and large, support whomever Democrats decide to run against Trump. The issue is turnout. After black turnout rates outpaced white turnout for the first time in history in 2012, they declined by 7 percentage points in 2016. However, according to an analysis by the Center for American Progress, if black voters in 2020 turn out at rates commensurate to 2012, the Democratic nominee can flip four key states away from Trump—Michigan, North Carolina, Pennsylvania and Wisconsin—and, most likely, win the election.

No one expects that Bernie Sanders will generate the same level of racial pride that swept Barack Obama into the White House in 2008 and again in 2012. So, what could Sanders do to boost black turnout to rates that rival 2008 and 2012?

Late last year, we sampled 1,545 black voters across the United States. The survey included a battery of questions about how likely they were to participate in the 2020 election in various ways—from what we called “conventional” (e.g., voting and donating) to “contentious” (e.g., protesting and boycotting). We divided the respondents into four groups. Three were presented with different messages about Trump before answering the questions, and the fourth, the control group, received no message. One message framed Trump as a threat to economic justice; one framed him as a threat to racial progress; and one framed him as a threat to American democracy. (A full description of the survey and its questions can be found here.)

Relative to respondents who received no specific political message, those who were primed with a message depicting Trump as a threat to racial progress were more likely to express confidence that they would participate in the 2020 election in a variety of ways, both conventional and contentious. But these results did not extend in a statistically significant way to those receiving the competing messages: Trump as threat to economic justice and to American democracy. (These results hold after adjusting for political and sociodemographic factors such as gender, age, income, education, region, ideology, partisanship, attitudes toward Trump and 2016 voter participation.)

In other words, our survey suggests that if Sanders—or whomever Democrats ultimately choose—wants to win over black voters, a message stressing economic justice is not the best option; he needs to appeal explicitly to race. This finding builds on emerging work showing that the perception of threat on the part of racial minorities can encourage political participation, as has been demonstrated in the Latino community. It also builds on our finding, published in a previous study, that holding negative opinions of Trump can be a mobilizing force for African American voters.

Why is a message emphasizing racism so effective, relative to the alternatives? Simply put, race is the principal identity that resonates with the black community. History makes clear that racism affects every aspect of African Americans’ lives, so much so that most members of the black community perceive that they share a common fate. This is not to say that class isn’t sometimes important, but when it comes to political engagement, racial identity is a more reliable predictor of black political behavior.

In 2016, Sanders was taken to task for not paying enough attention to racial issues and criminal justice reform. Leading into Super Tuesday in the previous election cycle, one of us predicted that Sanders would “burn out in Dixie”—and he did, before losing the primary. To his credit, this time around, the senator has stressed issues of race and racism more frequently on the campaign trail. In the Nevada caucuses, Sanders’ share of the African-American vote increased by 5 percentage points—from 22 percent in 2016 to 27 percent this year. But his performance among black voters in the South on Super Tuesday was hardly better than it was in 2016.

Let’s face it, Biden isn’t so great on race, either. His support of the controversial 1994 crime bill, as well as his opposition to busing in the 1970s, should give pause to anyone who thinks of him as a committed racial progressive. But Biden has some built-in advantages over Sanders: He was vice president to the first black president, and his moderate politics are generally seen as making him more electable than Sanders. Black folks, given Trump’s threats to racial progress, want him out of the White House in the worst way.

The map doesn’t get much easier for Sanders in the next round of primaries; in several upcoming states, the black community is key. No one expects him to abandon his long-held economic message, but if he wants to increase his support from black voters, he needs to pay more attention to race and racism. Otherwise, his revolution will soon fail again.