Bernie Sanders has had strong showings in Iowa and New Hampshire, but he is facing an important challenge: appealing to minority voters. Voters in the Democratic contests were more than 90 percent white. But that changes in the upcoming contests in Nevada and especially South Carolina, where almost 30 percent of the population and a majority of Democratic voters are black.

Our new research confirms what many Sanders supporters have feared: Black voters have substantially more favorable feelings about his opponent, Hillary Clinton.

Our data are unusual: a Jan. 22-Feb. 13 survey of approximately 1,100 African Americans, conducted by the firm Survey Sampling International. Most polls at both the national and state level have to rely on small samples of black voters, and journalists are often forced to extrapolate minority voters’ views and preferences from interviews.

We found that blacks’ evaluations of Clinton were much more positive than their evaluations of Sanders. We asked respondent to rate the candidates on a “feeling thermometer” that ranges from 0 (very unfavorable) to 100 (very favorable). The graph below displays people’s responses.

On average, blacks gave Clinton a 72 and Sanders a 58 — only slightly above the neutral point. Among blacks who are registered to vote and know where to vote, Clinton’s advantage grows further.

Is there any evidence that Sanders is making inroads with at least some groups of black voters?

For example, much has been made of Sanders’s popularity with younger voters, and Clinton’s struggles to connect with millennials. Among black voters age 18-29, the gap between Sanders and Clinton is indeed narrower. But younger black voters still rate Clinton more favorably than Sanders:

Perhaps most troublesome for Sanders, however, is the ambivalence toward him expressed by black women. Black women comprise a disproportionate segment of the black electorate — due in part to laws in some states preventing ex-felons, many of them black men, from voting.

According to the U.S. Census, turnout among black women in 2012 was almost nine percentage points higher than turnout among black men — a gender gap larger than the gender gap among Hispanics, Asians, and non-Hispanic whites. Moreover, black women tend to vote for Democrats at even higher rates than black men.

In other words, a Democratic victory in the general election requires enthusiastic support from black women, and black women are significantly more enthusiastic about Clinton than Sanders.

We also find that, unsurprisingly, black voters are not enthusiastic about any of the potential Republican nominees. Donald Trump touts his popularity in the black community, asserting “…The African Americans love me because they know I am going to bring back jobs. … They are going to like me better than they like Obama.”

But in our data, blacks rated Trump a dismal 22, significantly below each of the other GOP contenders we asked about, including both Ted Cruz and Marco Rubio, who were each rated quite negatively but less so than Trump.

Taken together, these results suggest good news for Clinton and bad news for both Sanders and especially the Republican Party. Black voters appear poised to give Clinton’s candidacy a significant boost in states like South Carolina. They’re even more poised to back any Democratic nominee against a set of Republican candidates that they greatly dislike.

Mackenzie Israel-Trummel is an assistant professor of political science at the University of Oklahoma. Ariela Schachter is a Ph.D. candidate in sociology at Stanford University.