http://www.washingtonpost.com/blogs/...cRwQ_blog.html
Obama: The most polarizing moderate ever
Posted by Ezra Klein at 10:04 AM ET, 02/07/2012

In 2011, Gallup’s polling showed that President Obama averaged an 80 percent approval rating among Democrats and 12 percent among Republicans, making his third year in office one of the most polarizing on record. For a candidate whose campaign promised an era of post-partisan unity, it must be a disappointing reality check.

But on Friday, political scientist Keith Poole released a study that probably cheered the White House. According to Poole’s highly respected classification system, Obama is the most moderate Democratic president since World War II. Which raises a question: How can Obama simultaneously be one of the most divisive and most moderate presidents of the past century?


(Keith Poole, VoteView.com)
Poole’s study is based on a system for sorting politicians known as “DW-Nominate.” But DW-Nominate doesn’t directly measure ideology. Instead, it measures coalitions. It’s got pretty much every roll-call vote taken between 1789 and December 2011. It looks to see who votes together and how often. The assumption is that the most ideological members of both parties will do the least crossover voting. And it works. Its results line up with both common sense and alternative ways of measuring ideology, like the scorecard kept by the American Conservative Union.

Over the past century, DW-Nominate has revealed a steady increase in congressional polarization. Democrats have moved to the left, while Republicans have moved to the right. But Republicans have moved a lot farther than Democrats.