Incumbency advantage concerns resources attached to holding office. Members of Congress often begin with name recognition, donor networks, staff, media access, and a record of constituency service. Strong prospective challengers may wait for an open seat, reinforcing the incumbent's advantage before campaigning begins. The pattern is not a guarantee.

Keep the three mechanisms separate even when they coexist. A representative can possess a real incumbency advantage and still lose during a national midterm wave. A popular presidential nominee can create coattails in one cycle, while the same party experiences a midterm penalty two years later.

Video lesson: Election Basics: Crash Course Government and Politics #36