This morning, in doing a little bit of remote-term planning for features that we might add to the site in the distant future, I was doing some background research on liberal-conservative scores and other methods of vote classification and stumbled across a website called voteview.com, created by a University of California at San Diego professor named Keith Poole. Voteview uses an extremely rigorous methodology for ordering Senators from most liberal to most conservative which to my mind produces some fairly intuitive results. (Five most liberal senators thus far this year? Russ Feingold, Chris Dodd, Bernie Sanders, Sheldon Whitehose, and Ted Kennedy).
This is how Voteview classifies Senators McCain and Obama over the last four Congresses; for good measure we'll also throw in Senator Clinton:
Congress Obama McCain ClintonBy this method, Obama is liberal, but not that liberal. He was the 21st most liberal senator in the 109th Congress and has been the 10th or 11th most liberal thus far in the 110th. The surprising result is John McCain, who rates as the 8th most conservative senator in the 110th Congress, the 2nd most conservative in the 109th, and the 5th or 6th most conservative in the 108th.
107th -- 57/102 22/102
108th -- 96.5/100 21.5/100
109th 21/101 100/101 25/101
110th 10.5/101 94/101 20/101
In the 107th Congress, however, McCain was quite moderate. Voteview doesn't have rankings before the 107th, so I'm not sure whether there was some permanent change in McCain's political philosophy on or around 2003 (perhaps coinciding with the start of the Iraq War) or whether it was his behavior in the 107th that was unusual (perhaps he took some pleasure in being a thorn in President Bush's side after having lost the primary to him). But this is more evidence for the notion that the 2008 version of John McCain is a very different politician than the 2000-2002 version of John McCain.