Does more registered Democrats mean more Democratic victories?

In 2004, there were roughly as many people registered as Republicans as there were registered as Democrats. This year, there are about 1.5 million more Democrats than Republicans. Will that necessarily translate into more Democratic victories? Probably. At least, if you ignore the south. But the answer isn't as obvious as you might think at first.

Since President George W. Bush’s re-election in November 2004, the Democrats have added more than 800,000 voters to the rolls, while the number of registered Republicans has declined by about the same amount, according to a compilation of recent registration data. Meanwhile, the number of voters not affiliated with either party — the prime “growth stock” among registered voters in the past decade or two — has dropped by nearly 200,000.

The critical question, though, is whether this will mean much in terms of voting in November.

In 2004, it did. At least that was the case outside the South, where the five states with party registration all voted for Republican Bush in spite of a lingering Democratic registration advantage.

Elsewhere, though, there was a strong correlation between a state’s party registration totals and the general-election outcome. Republicans out-registered Democrats in 10 of the 12 non-Southern party registration states carried by Bush (with New Mexico and West Virginia the two exceptions). There were more registered Democrats than Republicans in 11 of the 12 party registration states won by Democrat John Kerry (with New Hampshire the lone exception).