This paper exploits the informational value of incumbency: incumbency confers voters information about governing politicians not available from challengers. We propose a measure of incumbency advantage that improves the use of pure reelection success. We also study the relationship between incumbency advantage, ideological bias, and terms in office. Our argument emphasizes that incumbency affects candidates' chances of winning even if they had no opportunity to strategically utilize policies. © 2009 Wiley Periodicals, Inc.