Bureaucratic Bias or Voter-Side Factors? Testing Competing Explanations for Racial Gaps in Vote-By-Mail Ballot Signature Rejections

Differential rejection rates of vote-by-mail (VBM) ballots by race and ethnicity are often attributed to voter-side factors—such as cultural or linguistic barriers—rather than to discretionary decisions by signature evaluators. We assess this claim with a two-part research design. In Study 1, an audit of Washington State ballot status reports revealed that ballots cast by voters with Hispanic surnames are substantially more likely to be rejected for signature mismatch than those cast by non-Hispanic White surnames, and that the disparity between mismatch and late-submission rejections is markedly greater for Hispanic voters, implicating administrative discretion. In Study 2, 1,797 Washingtonians evaluated 24 pairs of valid signatures—each bearing a Hispanic- or White-coded name—produced by volunteers from diverse racial and ethnic backgrounds who were randomly assigned to each name, thereby neutralizing systematic voter-side factors. Evaluators rejected Hispanic-named signatures at higher rates than White-named ones. Supplementary analysis reported in the appendix shows that an explicit pro-White/anti-immigrant bias measure predicted lower acceptance of Hispanic-named signatures but had no effect on White-named signature acceptance. Overall, the accumulated evidence implicates evaluator bias as the primary driver of racial disparities in VBM signature verification and calls for reforms that can mitigate such bias to ensure equitable election administration.