See How They Run.

While party control of the legislatures has become more and more competitive over the last 30 years, hundreds of seats go unchallenged in every election.

In fact, individual legislative seats are much less competitive today than they were in the 1970s.

There are two ways to measure competitiveness. One is by how many seats have both a Republican and Democrat candidate running (contested seats). The other is how many races are close (the winner gets less than 60 percent of the vote).

From the mid-1970s to the late 1980s the proportion of uncontested seats increased significantly, while the number of close races declined. The redistricting election of 1992 and the "Republican revolution" elections of 1994 and 1996 caused an increase in competitiveness, but not back to the highs of 1970 through 1976.

Looking in more detail at each state in the 1990s shows that the highly competitive states of New York, New Jersey, California, Michigan, Minnesota, Nevada and Ohio have...