Election integrity is a cornerstone of democracy. In the US, voters who move will often have active registrations in more than one state, opening up the possibility that they can choose where to vote. This raises fairness concerns. This column uses the universe of US voters in 2020 to measure the number of double-registered individuals and their characteristics. Double registrants respond to cross-state strategic incentives and costs. They disproportionately choose to vote in swing states and