A New Measure of Party Strength

In order to measure the strength of the parties in each state, the Major Party Index (MPI) was built by averaging the results of the six major elections that take place in the fifty states. This index allows us to describe the absolute and comparative partisan leaning of each state in each election and identify trends of party strength over time within individual states, among regions, and within the nation as a whole. The MPI sheds considerable light on three general developments: (1) a national change from Democratic dominance in the 1980s to a Republican edge by 2002, (2) significant regional realignments in the South and New England, and (3) a strong trend toward greater consistency between partisan voting at the federal and state levels.