Why Incumbents Lose, Part One

Change in politics comes in two ways: contests for open seats and successful challenges to incumbents. The former happens all the time while the latter is more rare. But barn-burning incumbent challenges can be some of the most exciting races ever. How often do they succeed?

We assembled election data for all forty-two state and county offices in Montgomery County over the last four cycles. Our finding is that of the last 126 races in which incumbents ran, they won 109 times – a win rate of 86.5%. But the incumbent win rate has drifted slowly downwards from 92.0% in 1994 to 81.3% in 2006. Here is our complete dataset.


We’ll take a shot at explaining the incumbent losses in Part Two.