Partisans in the American electorate are affectively polarized, which coincides with the tendency for partisan geographic sorting. Could mate selection pressures contribute to this geographic tendency, and how might they interact with out-party affect? I propose a model in which an individual's perception of their mate success in a niche is key. I argue that perceived mate success is a function of a niche's partisanship and one's out-party affect, which in turn, incentivizes sorting. The model is partially tested with conjoint experiments on multiple U.S. samples. Results show that partisans perceive a lower probability of mate success in niches with greater shares of out-partisans and that mate success interacts with negative out-party affect. I also replicate findings on political mate choice preferences with a more appropriate method. Lastly, this project links instrumentality and affect, which is a departure from past work. In doing so, it contributes to research on the consequences of mate pressures for political behavior.