The left panel shows a House vote to raise the debt ceiling from 1981. As you can see, neither ideology nor partisanship played much of a role. The right panel shows the partisan vote from last year (I say partisan because ideology doesn’t explain the negative vote choices of Democrats very well). Note the gap between the parties. I patched the graphs together from “Keith Poole”:http://www.voteview.com/’s site. For much more analysis, including a “simulation of how debt ceiling votes have become polarized since 1981”:http://voteview.spia.uga.edu/images/debtceiling.gif and a predicted 2011 vote, see the “Voteview blog”:http://voteview.spia.uga.edu/blog/?p=1494.
**Update:** I should explain more clearly what the graphs show. The x-axis is liberal-conservative ideology of House members, estimated from their votes on all issues (the links to Keith Poole’s website explain this in more detail). The gap in the right panel thus signifies that the most conservative Democrats and the most Liberal Republicans are far removed from each other in 2010.