Vote View tracks the Republican lurch to the right:
We have previously written about asymmetric polarization, arguing that the primary driver of contemporary partisan polarization has been the steady movement of congressional Republicans to the right. This trend appears to have continued through the 112th congress. House Republicans – despite a large majority earned in the 2010 midterm elections – have continued their rightward drift, adding more conservative members than moderate members. Senate Republicans also became a more conservative group in the 112th Congress, while Senate Democrats remained mostly ideologically static.