U.S. Politics One Dimensional

Matt Yglesias commenting on a Paul Krugman post:

To offer some qualitative examples, Susan Collins and Olympia Snowe are pro-choice Republican Senators. But they’re also the two senators who seem like they might possibly vote for a national health care bill. Rather than representing some kind of ideal type of upscale northeasterner who’s socially liberal but economically conservative, they’re less conservative across-the-board than their colleagues from the South and the Mountains. Conversely, when you stroll down to Arkansas’ Democratic Senators, you don’t see cultural conservatives with populist economics, they’re just more conservative across-the-board than their coastal colleagues.

It's nice to think there'd be some more nuance to it, but apparently not. It looks like the only time there was a second dimension was civil rights. What's the reason? Neither Yglesias nor Krugman speculate, and I'm no political scientist... I'd be curious to see data from some European parliaments. What does the increased polarization lead to? Gridlock. Nothing gets passed, which is handy when you're in the minority party and annoying when you want health care reform passed.