Anyway, the idea is this: If there really is something unique about sixth-year elections, then an added variable denoting elections occurring in a sixth year — 1966, 1974, 1986, 1998, and 2006 — should come back statistically significant as well.
It doesn’t. In fact it isn’t particularly close (for those stats geeks in the audience, the p is 0.56). This suggests that sixth-year elections don’t behave any differently than any other sort of congressional election.
So what does all of this mean for 2014? Well, we know that the election should be governed by traditional factors: the economy, the president’s popularity, how overexposed the party is. The fact that it is a sixth-year election is, by itself, pretty meaningless.
But we should also bear in mind that the fact that the Democrats got walloped in 2010 means that it would be highly unusual for factors to coalesce and create a really bad year again in 2014. This should put a damper on Republican expectations for 2014, and give Democrats some hope that they can make some gains, even if picking up the 17 seats needed to take the House is probably out of reach.