Abstract
I examine competing explanations for House rules changes with significant partisan overtones. I sought to identify all rules changes adopted from 1867 to 1998 that were intended either to advantage or to undermine the majority party and its leaders in their efforts to shape the House agenda. I test a majority party cartel model of institutional change against a model that focuses on the ideological balance of power on the floor, that is, on the closeness of the median voter to the median member of the majority and minority parties. I also evaluate the conditional party government approach. The data analysis suggests the preeminent importance of shifts in the ideological balance. Two variables identified by the conditional party government theory, party polarization and party capacity, obtain limited support, but their effect is neither as robust nor as large in magnitude as that of change in the median voter's position.