[tstew]

Just out of curioisity, I went to the National Journal study where they found Obama to be the most Liberal Senator. I wanted to find out more about the criteria. It is interesting reading. He does vote as Liberal on many key issues. He did cross and vote with the conservatives on funding the military.
But I also found this that I thought was curious, in order to get ranked you have to vote on a minimal number of issues I guess to establish a pattern:

"Sen. John McCain, R-Ariz., the only other senator whose presidential candidacy survived the initial round of primaries and caucuses this year, did not vote frequently enough in 2007 to draw a composite score. He missed more than half of the votes in both the economic and foreign-policy categories."