Can abortion ballot measures generate electoral spillover effects, and for whom? Abortion ballot measures have become an important aspect of US elections, with 16 states voting on measures since the 2022 Supreme Court ruling in Dobbs v. Jackson Women’s Health. Using nationwide electoral returns and survey data, we study the effects of abortion ballot measures on election outcomes in 2022 and 2024. We find no evidence that abortion ballot measures increase overall turnout. Results show that abortion ballot measures decreased the Republican vote margin in US House elections by 4.9 percentage points in 2022 but increased the margin by 4.5 percentage points in 2024. The increase in Republican votes in 2024 can be explained by a vote separation mechanism: ballot measures allow voters to separate the specific ballot issue from their choice of partisan candidate.