PVI refers to the House district-level partisan performance of presidential candidates. For example, in 2004 John Kerry carried 179 districts. He also won 19 states plus the
- Of the 435 districts, 352 were carried by the same party as the presidential candidate. Barack Obama and the Democratic candidate won 208 of those, and John McCain and the Republican candidate won the remaining 144.
- That leaves 83 districts with cross-partisan results—what POLIDATA calls McCain Democrats (MD) or Obama Republicans (OR). There were about half again more of the former (49) than the latter (34).
But all else may not be equal. Counting districts simply as “McCain Democrats” or “Obama Republicans” does not indicate either the margin of victory for those incumbents or the opposite party’s presidential candidate. Nor does it consider idiosyncratic factors like state and local politics, and the strength of individual incumbents.
I’ll drill down into that a bit more in subsequent posts.