Research shows that ethnic minority candidates often face an electoral penalty at the ballot box. In this study, we argue that this penalty depends on both candidate and voter characteristics, and that pro-minority policy positions incur a greater penalty than a candidate’s ethnic background itself. Using a conjoint experiment embedded in a panel study of British voters, we investigate the relative contributions of candidate ethnicity, policy positions, affirmative action, and voter attitudes to this electoral penalty. We find that although Pakistani (Muslim) candidates are penalized directly for their ethnicity, black Caribbean candidates receive on average the same levels of support as white British ones. However, black Caribbean candidates suffer conditional discrimination where they are penalized if they express support for pro-minority policies, and all candidates are penalized for having been selected through an affirmative action initiative. We also find that some white British voters are more inclined to support a black Caribbean candidate than a white British one, all else being equal. These voters (one quarter of our sample) have cosmopolitan views on immigration, and a strong commitment to anti-prejudice norms. However, despite efforts across parties to increase the ethnic diversity of candidates for office, many voters’ preferences continue to pose barriers toward descriptive and substantive representation of ethnic minority groups.