The collapsing dimensions of American politics

What is that supposed to mean?  Well, first off, my apologies for being a pretty lame blogger lately.  Busy start to the semester and the busiest teaching schedule I’ve had in a while.  Also, so much I want to say about so many things that I kind of end up saying nothing at all.  I’ll try and be better.  Probably shorter posts, but more.  Can’t just put everything in quick hits.

Anyway, on to my point.  Some very smart political scientists have been mapping the votes of Congress on multiple dimensions for years with some interesting results.  Most, but far from all, of Congressional votes could historically be explained by the first, scope-of-government, left-right dimension.  We’ve now reached a point where most everything can be explained by a single dimension– Democrat vs. Republican, and that’s it.  And that’s not good.  From VoteView:

What we find alarming is the unprecedented collapse of the long-term structure of Congressional Voting during the past 20 years. [emphases mine] Contrary to what many scholars say when they cite our book, Congress: A Political-Economic History of Roll Call Voting (1997, New York: Oxford University Press), Poole and Rosenthal DO NOT CLAIM that voting in Congress is largely one-dimensional. Rather Poole and Rosenthal show that a two-dimensional dynamic spatial model is the best fitting model for Congresses 1 – 99.

What has happened in the past 20 years is that the second dimension of Congressional voting has slowly evaporated. As late as the 1990s the second dimension picked up differences within each of the parties over abortion, gun rights, and other social or lifestyle issues. For example, on the vexed issue of abortion each Party had a pro-choice and a pro-life faction. Hence, roll call votes on Abortion often cut through the parties along the second dimension. The same was true for gun control (see the spatial maps in this post). Hare and Poole show the second dimension disappearing in a variety of issue areas in this analysis.

The two figures below show that the extraordinary divisiveness that has marked American Politics since November 2000 has resulted in Congressional voting to collapse into a one dimensional near Parliamentary voting structure; that is, the parties are very unified as shown by Party Unity Scores. The first graph shows the correct classification for each House in 10, 2, and 1 dimensions using Optimal Classification. Note the dramatic convergence of all three measures during the past 20 years. This shows that almost every issue is voted along “liberal-conservative” (it is hard to make sense what this dimension means any more!) lines. Furthermore, no other period in American history shows this pattern.

Donald Trump will be the third consecutive President who is widely disliked by members of the opposite Party. Indeed, Trump’s personality coupled with the extraordinary party unity within each party will mean that American Politics will enter a phase that has never been seen before. We hope things do not melt down but we would not bet our mortgages on it!

Now, of course, this does not portend bad things, but it is certainly unprecedented, so we could have unprecedented bad outcomes in our politics.  Or, maybe things will be unprecedentedly good and America will be great again in no time!


About Steve Greene
Professor of Political Science at NC State

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