Annual vote ratings show he shifted further to the left last year. Ranked as the 16th- and 10th-most-liberal during his first two years in the Senate.
Clinton also shifted more to the left, ranking at number 16, after being number 32 in 2006.
Response from Obama spokesman Burton: "Only in Washington can you get falsely attacked for being like Reagan one week and labeled the most liberal the next." Read full statement.
