Our new spatial voting model explains why congressional candidates adopt more extreme ideological positions than their constituents' preferences. Unlike standard models, we find that voters in the candidate's own party tolerate extremism without imposing electoral penalties.

This voter tolerance creates "leeway" for candidates to take extreme stances because they increasingly rely on same-party supporters. Our findings show this explains overall candidate polarization without needing institutional factors like primary elections.

Key insights include: • Voters in the candidate's party accept extremism • This tolerance creates electoral leeway • Polarization occurs independently of primaries

Electoral simulations demonstrate that perceptual bias asymmetry is one mechanism explaining this phenomenon. Our analysis confirms real-world patterns of ideological representation align with these simulation results.