Bellwether State Law and Legal Definition
Bellwether state is a state which, historically, tends to vote for the winning candidate, perhaps because it is demographically a microcosm of the country as a whole. The classic example of a bellwether state is Missouri, which has voted for the winner in every US presidential election since 1904 - except 1956.
The term derives from the name for a sheep which shepherds would fit with a bell. By listening out for this sheep, the bellwether, shepherds were able to locate the position of the entire flock. Bellwether is any entity in a given arena that serves to create or influence trends or to presage future happenings.