Ryan O’Donnell explains the above chart, which shows the relationship between political districts’ ideology and their representatives’ votes:
Obviously we’d expect Democratic politicians to vote more conservative the more conservative their district gets, and more liberal the more liberal their district gets. And by-and-large, they do. But Republicans don’t really follow that trend, as you can see in red on the graph [above] … If you only take away one thing from this graph, it should be that the expected value for Republicans is nearly a perfect horizontal line. Translated into plain English, that means Republicans vote conservative almost no matter what. It doesn’t matter what type of districts they represent.
The lesson Matt Steinglass draws from this:
This doesn’t predict what might happen if Republicans gained control of the Senate, or of the presidency. It’s possible that with more power Republicans would feel freer to disagree with each other. With their backs to the wall, out-of-power Democrats might feel the need to present a more united front. But basically Democrats have less voting discipline than Republicans. …
In other words, if all else fails, the gridlock of the American government will probably end the next time the country elects a Republican president, since Republican legislators have the discipline to stonewall Democratic presidents while Democrats are more willing to compromise. That asymmetry is probably infuriating to Democrats, but unless their legislators adopt different voting behaviour, it’s not going to change.