In the aftermath of the 2006 election, the era of polarization was declared over in such astute analyses as this one:

The impetus behind such conclusions was the extraordinary success of “Red State” Democrats such as Jon Tester and Heath Shuler. But few pundits took note of the fact the these Red Democrats were only moderate or conservative on a few social issues, but quite populist on economics and trade. Even fewer considered the consequences of the extinction of “Blue State” Republicans for polarization in Congress.

But now that Congress has adjourned sine die, Keith Poole has fired up the NOMINATE machine, and we can look at what impact, in any, the 2006 elections had on the level of party polarization in the House and Senate.

This first figure is an update of the data presented in our book with Howard Rosenthal showing the average difference between Democrats and Republicans on the DW-NOMINATE conservatism scale.

Do you see the dramatic collapse of polarization in congressional term beginning in 2007? Me neither. In fact, polarization rose in the 110th Congress just as it has almost every term since 1975. The House had set a record for polarization in the 109th, but the 110th broke it. The Senate broke its own record set in 1867.

So what might the future bring? To get a prediction that is hopefully at least as accurate as Joe Klein’s, I have forecast the average conservatism of Democrats and Republicans for the next congressional term in the following way:

1. Assigned all returning members their DW-NOMINATE score from the preceding term.
2. Assigned all new members the average DW-NOMINATE score for their party and region. In other words, a new Democrat from the Midwest gets the average of all midwestern Democrats and a new Republican from the South is assigned the average of all southern Republicans.

Essentially, this procedure captures the effects of the regional distribution of partisan seat shifts. A seat shifted from Republicans to Democrats in the Northeast increases polarization whereas a Democratic pickup in the South decreases it. So here is what the House and Senate may look like next term.

In each of the figures, the red line is the average conservatism of Republicans, and the blue line is the average conservatism of the Democrats for each term since 1969. The triangles are my prediction for the next term. The Democratic average is expected to change very little, but the Republicans will be considerably more conservative. This, of course, is due to their continued hemorrhaging of seats outside the South. The net effect is again an increase in polarization.

All of this is predicated on the assumption that there will not be any major deviations from recent historical patterns. Of course, things could change. In the conclusion of our book (written in January 2005), Keith, Howard, and I speculate that a financial crisis triggered by a housing bubble might lead to a swing in the public’s partisanship and ideology that might cause the Republicans to moderate. So we have the crisis, a modest swing in public attitudes, but if the congressional votes on the bailouts are any indication, the Republicans haven’t take that last step.