In the period since the Reagan revolution that disrupted decades of Democratic control of the United States Senate, Democratic senators have proved remarkably resilient when running for reelection. Over the past 600 Senate elections since 1980, Republican incumbents have been defeated at more than twice the rate of Democrats, but won open seat elections at a significantly higher rate. This partisan disparity also appears in incumbent vote share, and is statistically and substantively robust to a range of model specifications accounting for existing theories. A series of explanations drawn from existing research explored in this paper fail to explain this trend, suggesting the need for future research targeting partisan differences in perceptions of parties in Senate campaigns.