The title is a failed attempt to show off my NASCAR creds. More fun polysci research to start off your week…
Of all the claims that the most alienated progressives routinely throw around, perhaps the most frustrating one is that there are no important differences between the two parties, or slightly less dismissively, that the Democratic Party is the lesser of two evils. In fact, political scientists are in agreement that the parties are ideologically more polarized today than at any time in the past 30 years.
The latest study to reinforce this conclusion comes from Sean M. Theriault in the latest issue of Party Politics. In “Party Polarization in the U.S. Congress,” Theriault shows that both parties have grown more ideologically extreme since 1973 and less diverse. He arrives at this conclusion using the well-regarded Poole-Rosenthal scores, which array all members of Congress from all years on an ideological scale based on the entirety of their voting record. Legislators are assumed to lie on an ideological continuum, as are voting options (yea or nay) for every vote. Each legislator chooses the option that is closest to them ideologically. Then scores are assigned to each legislator and vote option so that the number of “errors” made is minimized (with errors occurring when a legislator votes contrary to what we would expect given the initial assumptions).
Theriault’s results shed light on the nature of growing political polarization and Republican power. In the House, the two parties were roughly equally distant from the center in 1973, but by 2003, Republicans were more extreme. Democratic senators started out more extreme than their Republican counterparts, but by 2003 the parties were equally extreme. Polarization was more pronounced in the House, and by 2003 House Republicans were more “off center” than Republican senators or Democrats in either body.
What accounts for these trends? Two-thirds of the rise in polarization was a consequence of more moderate members being replaced by more extreme ones, either as the former died or voluntarily left their office or as a result of being defeated. The key elections on the House side were in 1972, 1984, 1994, and 1996, while on the Senate side polarization due to replacement jumped in 1972, 1980, and 1992.
What is more, much of this “replacement” involved Republicans succeeding southern Democrats. About 40 percent of greater polarization in the House was due to this phenomenon, and 45 percent in the Senate. Otherwise, in the House, 24 percent of polarization growth was due to replacement of moderates by more extreme members of the same party — particularly consequential on the Republican side. On the other hand, in the Senate, 25 percent of increased polarization arose due to instances where the incumbent was defeated but that did not involve a southern Democrat losing to a Republican.
Finally, about one-third of the increase in polarization was due to individual members’ increasing extremism over time. Increasing GOP extremism accounted for about one-fifth of the increase in polarization, while growing Democratic extremism accounted for 16-17 percent of the increase. Increases in legislators’ extremism after 1980 were particularly consequential in the House. Indeed, of the representatives with the ten biggest career-spanning increases since 1973, five are current members of the House.
The take-away point from the perspective of the Strategist is that the realignment of southern Democrats toward the Republican Party is the most consequential electoral development both for political polarization and for GOP power. Indeed, it is quite possible that this replacement phenomenon actually drove the changes in individual members’ ideologies that further increased polarization. On the Republican side, greater conservative representation weakened the hand of moderates and pressured them to toe the (increasingly right-wing) line. On the Democratic side, a stronger and more unified GOP may have led some legislators to moderate their views in an effort to win back swing voters. Hence, extremism grew less among Democrats than Republicans. But it still grew, and so the likelihood of keeping (or winning back) Congressional majorities has grown increasingly uncertain over time.
The result, one might argue, is a 51-49 Nation, resting at a right-of-center equilibrium corresponding to the professed ideological position of American voters. Of course, Democrats may win back one or both chambers of Congress in November, thanks to GOP incompetence and ideological over-reach. But there is little sign of a realignment back in favor of Democrats, so close elections will continue to be the rule until one of the parties breaks out of what Stan Greenberg has called the “Two Americas” paradigm or until outside events shift public opinion decisively.