As a whole, House Republicans are the most conservative they've been in 100 years.

The VoteView blog tracks the ideological leanings of Congress and finds Republicans are further to the right than they've been in the last century.

Democrats in the House have moved to the left, but they are not as far to that extreme as they were in the late 1800's.

Senate Republicans and Democrats have also moved away from the center, but not as dramatically.

Both figures indicate that the median Republican and Democrat has moved towards their respective ideological poles in the contemporary period, but this effect is considerably larger in the House than the Senate and for Republicans more than Democrats. Because of this and the fact that partisan control of the House has become more volatile in the recent past (prior to 1994, Democrats controlled the House for forty years), the chamber median in the House has become much more volatile. This is important because the median member of the House can be thought of as “pivotal“: the difference between a winning 218-member coalition or a losing 217-member coalition. As a consequence of two polarized parties–neither of which are likely to assemble long-term governing coalitions–policy swings are more frequent and dramatic.