McCain, Most Anti-Social Republican in Congress
I have a great deal of respect for the Professors who put together VoteView. They say that over 90% of votes in Congress are one-dimensional, either more government or less. Race, they say, was a strong second dimension in the 1950s through 1980, but no longer is. Their current second issue is called "Social/Lifestyle Issues". According to the graph below, linked to at their page discussing the rankings of Obama, McCain and Clinton, McCain is the most conservative of any Democrat or Republican on social and lifestyle issues. "S" refers to Southern Democrats.