The article explains the incumbency advantage by examining how incumbents signal their ideological positions differently than challengers. It uses voter-level data from the Cooperative Congressional Election Study and accounts for unobserved district heterogeneity.

📊 Voter Perception Mechanisms:

• Incumbents rely on individual candidate ideology to establish party alignment
• Challengers are primarily identified through party affiliation in House races, but less so in Senate contests

🔍 Signaling Decomposition:

The study breaks incumbency advantage into components. Results show:

• Ideological signaling accounts for 14% of the advantage in US House elections
• This mechanism explains only 5% of the advantage in Senate races

⚖️ Policy Implications:

A 50% increase in party polarization boosts the incumbency gap by approximately 3 percentage points.