To distract myself from the intense desire to scream while listening to Sen. Jon Kyl (R-AZ) speak at the health care summit, I read a fine post by Nate Silver that explodes the myth that incumbents who don’t hold a majority in early polls are already toasty if not toast. This myth is being used by Republicans to declare a lot of Democrats as walking dead long before campaigns actually develop. Turns out, though, the available evidence doesn’t support that proposition. Here’s Nate’s conclusion:
1) It is extremely common for an incumbent come back to win re-election while having less than 50 percent of the vote in early polls.2) In comparison to early polls, there is no demonstrable tendency for challengers to pick up a larger share of the undecided vote than incumbents.
3) Incumbents almost always get a larger share of the actual vote than they do in early polls (as do challengers). They do not “get what they get in the tracking”; they almost always get more.
4) However, the incumbent’s vote share in early polls may in fact be a better predictor of the final margin in the race than the opponent’s vote share. That is, it may be proper to focus more on the incumbent’s number than the opponent’s when evaluating such a poll — even though it is extremely improper to assume that the incumbent will not pick up any additional percentage of the vote.
Nate goes on to say that a much narrower version of the “50% incumbent rule,” which focuses on polls taken late in an election cycle, has more merit, but isn’t really a “rule” either. On the other hand, incumbents who register at above 50% in early polls do typically win. This ought to be kept in mind by Republicans who are fantasizing about a late “wave” that will sweep popular Democratic incumbents (and there are some) out of office.
This item is cross-posted at The Democratic Strategist.
