Political parties in the Senate are almost as polarized at they are in the House. Nevertheless, the explanations for party polarization work better for the House than they do the Senate. The growing polarization literature has speculated, though not precisely measured, the direct influence House polarization has had on the Senate. This paper finds that almost the entire growth in Senate party polarization since the early 1970s can be accounted for by Republican senators who previously served in the House after 1978. In turn, our analysis indicates that the impact of these Republican former representatives can partially be accounted for by a set of constituency factors that are related to their increased conservative voting.
That is from a new paper by Sean Theriault and David Rohde. (See also this piece by Sean at the Huffington Post.) “Gingrich Senators” is thus just a shorthand for those who joined the House after 1978, when Gingrich was elected.
Their thesis, slightly elaborated, is this:
It finds that the growing divide between the voting scores of Democrats and Republicans in the Senate can be accounted for almost entirely by the election of a particular breed of senator: Republicans who were previously elected to the House after 1978. It is the replacement of retiring or defeated senators (both Democrat and Republican) by these newly elected former House Republicans that single-handedly can account for almost the entire growth in the divide between Democrats and Republicans in the Senate since the early 1980s.
The reason is that these Senators were strong conservatives who essentially imported the hardball tactics they learned in the House during this era. Theriault and Rohde quote Alan Simpson on this score:
The rancor, the dissension, the disgusting harsh level came from those House members who came to the Senate. They brought it with ‘em. That’s where it began.
Here is a graph that shows how much the Gingrich Senators have contributed to Senate polarization:
Theriault and Rohde write:
From the 99th Congress to the 110th Congress (1985- 2008), the contribution of non-Gingrich Senators increased 0.2 percentage points each congress. The contribution attributed to Gingrich’s former colleagues, however, was five times greater (1.0 percentage points each congress). Again with this measure, the Gingrich Senators can account for the lion’s share of the Senate polarization over the last 36 years.
The differences between Gingrich Senators and others can only partially be explained by the characteristics of their respective constituencies. No other factor seems important, leaving Theriault and Rohde to hypothesize that their singular character may truly derive from their “baptism” in the more partisan House.