Ideological Cartography

As far as legislatures go, the U.S. congress has relatively stable legislative ideology. Most members of Congress adopt an ideological position upon entering Congress and maintain it for the remainder of their careers. Rarely do we see dramatic ideological shifts, and when we do, there is usually a story to explain the change—e.g. Senator Wayne Morse. This is not the case for many legislatures outside the U.S.. The French Fourth Republic was perhaps the best example. A chaotic legislature in constant motion, the National Assembly of the French Fourth Republic was well known for its dynamism and instability. A major contributing factor was the prevalence of party switchers. In fact, almost 20 percent of legislators switched parties one or more times between 1946 and the Fourth Republic’s collapse in 1958.

Below is an animation constructed from a dynamic optimal classification scaling with smoothed legislator estimates. Despite the fact that the French Fourth Republic is characterized by highly ideological voting, legislator ideal points were often subject to change, as only a fraction of members held consistent ideological positions for the duration of their careers.

(Maximize the video for best viewing. The roll call dataset is courtesy of Howard Rosenthal and Erik Voeten and is available for download here. The paper on the dynamic scaling method is available for download here.)

Watching the legislators in motion is quite a sight and makes the U.S. Congress seems somewhat boring in comparison. I’m not much of an expert on mid-twentieth century French politics, so I don’t have much commentary to add to the animation.  Although, a few things to look for are 1) early party positioning and legislator sorting in the first legislature and 2) the rise and collapse of the Gaullists during the second legislature.