Perhaps it’s a little too far past the cocktail hour to engage in this kind of overly general speculation, but I have a theory about why Democrats are doing so much better in Senate races and House specials than in regular House races (and probably also local/state races, though I don’t have any data to suggest that is true). The reason is simple: Democrats have better candidates.
In a typical House race, most people in the district don’t scrutinize the candidate that closely, but in Senate races and House special elections, candidates get a lot of media attention. Democrats won the Senate races in Nevada and Delaware largely on the basis of the fact that voters thought that the Republican candidates were weirdos. In the special races in NY-26, NY-20, and NY-23, Democrats were helped greatly by the fact that Hochul, Murphy, and Owens came across much better than Corwin, Tedisco, and Hoffman. Only Hoffman was a true nut among the Republican candidates, but in all three cases, the Democrat was, if not the person you’d rather have a beer with, then the person you’d trust more to help you do your taxes.
This is why I think that NY-26 may not be as good an omen for Democrats as it might appear at first blush. Democrats will generally field better candidates than Republicans in House races in 2012, but they won’t get as much mileage out of it as they would in a special election or a Senate race.