A Note on Gallup's Party Identification Map

Today, Gallup released its results of partisan identification in the 50 states. The results are, as usual, interesting.

This map does not correspond with the national presidential map terribly well, in that it underestimates Republican electoral strength. Why is this?

Part of the issue probably has to do with the evolution of American partisanship. You'll note that most of the "Republican" states are in the Great Plains: Kansas, Nebraska, South Dakota, Wyoming, Montana, Idaho, and Utah. These states have historically been Republican since they were brought into the Union. Actually, many of them were brought into the Union in 1889. The Republicans had control of the presidency and both chambers of Congress, and quickly added these states, which they believed would vote staunchly Republican.

They voted for Bryan in 1896 and Wilson in 1912 and 1916, but otherwise they were staunchly Republican up through the Great Depression. Kansas, Nebraska, and the Dakotas were the first Roosevelt states to peel away from FDR's coalition, voting Republican as early as 1940. And while Harry Truman did well in this part of the country in 1948, they have been pretty reliably Republican since 1952.

These states are thus but a handful that have moved very little in over 100 years in terms of party alignment. Most other states have moved from one side to the other - Vermont used to be the most Republican state and South Carolina used to be the most Democratic. Now, as Gallup finds, it is basically reversed. Even within states we often find major changes: Democrats used to do well in Western Pennsylvania and Southern Illinois while Republicans were strong in Eastern Pennsylvania and Northern Illinois, but now both intra-state trends are reversed.

(Original here.)