What explains the votes of U.S. senators to approve presidential nominees to the U.S. Supreme Court? Previous research has emphasized the roles that ideology and qualifications play while paying less attention to the role of partisanship. Through use of 22 nominations and 2000 Senate votes, regression analyses were estimated to determine whether there is a difference in considerations of Republican and Democratic senators, or senators of the same party and opposing party to the president, when casting confirmation votes. While both Republicans and Democrats consider qualifications most heavily when casting their votes, Republicans weigh ideology more heavily than Democrats. Additionally, senators of the opposing party to the president weigh qualifications more than ideology. In an era of heightened partisan polarization, these results have important implications for our understanding of the Supreme Court nomination process and the role of partisan considerations in the separation of powers.