Incumbents don’t go down very often, but they do go down. Of the last 126 races in which an incumbent ran in Montgomery County, 17 lost. Why do they lose their seats? We took a shot at answering that question, aided by some of our shrewdest and trustiest spies.Partisan RacesAs recently as the 1990s, the GOP was a viable minority party in Montgomery County. They tended to be concentrated in