Proven voter fraud in U.S. federal elections is extremely rare, based on multiple independent studies, state audits, DOJ reviews, and databases from groups like the Heritage Foundation and Brennan Center.
Estimates range from 0.000003% to 0.0025% of ballots cast, with Heritage's sampling showing ~1,600 cases over 40 years amid billions of votes. No credible evidence indicates rates high enough to alter federal outcomes.