Matthew Yglesias comes to the utterly unremarkable finding that the House Republican Leadership is deeply polarized. Except that he misinterprets the data. A lot.
DW nominate is a simply score of voting behavior. It’s based on an economic theory called “Spatial voting theory”.* Every time 2 congress members vote together, they move in the same direction. Every time they vote separately, they move apart. It adds a nice visual flavor to dry statistics, and there are a ton of books on the subject. DW nominate can tell you is how often a members of a party act in concert with one another. What it can’t tell you is how “right wing” or “left wing” a person– or party– is.
For example: Assume every Republican votes A) against an individual mandate for healthcare, and B) for Universal Healthcare, and Every Democrat votes A) For the individual mandate, and B) for universal Healthcare. We’d see every member of congress take 1 step away from every member of the opposite party**. This would be an extremely polarized congress, but not one that fits into anyone’s definition of the Right/Left divide.
What we expect to see in caucus leaders is that they tend to vote the same way they’re instructing their caucus to vote. The fact that there are people in the GOP caucus who voted with the caucus more than the leadership is interesting– and may explain why the house GOP had so many troubles over the last two years. But this data does not say that the GOP is moving rightward. We’ll have to look elsewhere for that…
* AKA: POL 100 at UC Davis.
**And incidentally end up with Universal Healthcare with an Individual mandate. Hooray!