Over the holidays, SSP readers seemed to have a lot of fun with the vulnerable House Republicans and vulnerable House Democrats threads. This left me wondering, as so many things seem to do, “is there a way to quantify that?” In other words, is there a data-driven way to approach the question instead of just relying on perceptions (and also to make sure that potentially overlooked races don’t fall through the cracks)?
Here’s what I tried. It’s actually a bit reminiscent of my PVI/Vote Index, in that it measures representative performance against the district’s lean, except here performance is measured by the rep’s margin in the last election. (The data for many of the 2008 electoral margins is available in the recent “How’d We Do?” post, conveniently arranged in order from closest to least close.)
Look at the top 20 most vulnerable Republicans to see how it works. As pretty much everyone would expect, Anh Cao in LA-02 is the most vulnerable GOPer. He had the 5th weakest margin of any Republican who survived 2008 (beating Bill Jefferson by 2.7%, behind only Fleming (0.4%), McClintock (0.6%), Calvert (2.4%), and Luetkemeyer (2.5%). Needless to say, he’s in the GOP-held district with the least favorable PVI (D+28, using “old,” i.e. 00-04, PVI). At #2 is Jim Gerlach in PA-06; he had the 9th worst margin at 4.2%, and he’s in the 6th worst district for a GOPer at D+2. And so on…
Is this much different from SSP readers’ predictions? No, not much; it’s the wisdom of crowds at work. Still, I see a few names on there that didn’t get much of any mention in our prediction thread: especially Pat Tiberi in OH-12 (34th worst margin at 12.6%, 14th worst district at R+1) who seems to fly under the radar every single freakin’ election. Other names revealed by this list that wouldn’t necessarily be intuitive picks include Thad McCotter, John Kline, Mike Rogers (AL), and Bill Posey, who benefited from our big-time recruitment failure in the FL-15 open seat.
Here’s the flipside: the Democratic seats that seem likeliest to flip, based on 2008 numbers. Some of these may not be much cause for alarm; Chet Edwards, for instance, is probably not in any imminent danger except in case of a 1994-sized event, but he’s probably doomed to uncomfortable margins for all eternity. On the other hand, time will tell whether Walt Minnick can quickly fortify himself, or if we’re only renting ID-01 for a couple years.
More over the flip…
In describing this method to DavidNYC, he quite rightly asked “Wait, does this thing actually work?” So, after a lot more data entry and some testing based on how well the 2006 numbers would have predicted the 2008 results, I can conclude it does work fairly well. Here is what the 2006 numbers would have predicted for GOP held seats in 2008.
One problem leapt out at me: the role of open seats, and the accompanying loss of the benefits of incumbency. So, I performed a tweak that took open seats into account (by taking out the margin, and just leaving the open seat’s strength based only on its PVI rating). That takes it a little closer to the way things actually shook out. 13 out of the top 20 were pickups, which seems like a good but not amazing rate of prediction.
Without doing a lot of putting your thumbs on the scales of individual races, I don’t know how you’d build a model that somehow predicted, say, Tom Feeney’s implosion, or the fizzle in the open seat in NM-02, or Dave Reichert’s confounding staying power, or Bob Roggio’s amazing lack of name recognition… or that Bill Sali was vulnerable (he was #106) if only because of sheer malice and stupidity. Any good prognostication has to include at least some kind of qualitative analysis of candidates’ levels of, well, suckiness.
By the way, in case you’re wondering what this formulation means would happen to Peter King’s seat if he bails out to run for NY-Sen, it would vault up to #2 on the list if it were open. (It’s the 7th most Dem PVI of any GOP-held seat, so for 2010 the score of 7 would slot an open NY-03 right before LA-02.) So, a year from now, once we have a sense of where seats will open up, I’ll have to revisit this project.
Finally, here’s what the 2006 numbers would have predicted for the Democratic-held seats in 2008, including the tweak for open seats (of which we didn’t have many). Three of the top 10 did, in fact, fall. Plus, LA-06 isn’t on the list because it changed hands during a special election. However, my back-of-the-envelope calculation for Cazayoux based on his 3% margin in the special election and an R+6.5 would’ve given him a score around 24, good for 4th place. On the other hand, the fifth Dem seat to fall, LA-02, clocks in at #187!