Chapter One
Two Clocks
Imagine a clock that empties its face every two years. All its markers must be put back by an election. Beside it stands a second clock with a slower movement. Only one of its three sectors comes due at the same moment. The clocks belong to the House of Representatives and the Senate, the two chambers of the United States Congress. Their hands meet at a congressional election, but they do not measure exposure to voters in the same way.
Every seat in the House is normally contested at each regular congressional election. Its members serve two year terms. Senators serve six year terms, and their seats are divided into classes so that roughly a third is contested every two years. The election held halfway between presidential elections is called a midterm. In a presidential year, the congressional clocks still turn. The distinction is the position of that congressional election within the president's four year term, not a special kind of ballot for the House.
The simple timing explains why a familiar headline can mislead. A party may win the most House seats and still watch the Senate remain with its rival. It may gain Senate seats and lose the House. The chambers answer different geographic questions as well. House members represent districts whose number in each state reflects population. Senators represent whole states, two per state. A shift in one chamber need not be repeated in the other, even when both sets of votes are cast on the same day.
