Who is the most liberal Democratic Presidential Contender?

The Washington Times has an article using the Congressional Quarterly "key votes" to see how the different Democratic presidential contenders compare with each other:

Another way of looking at these five senators is to compare how often each of them agreed with Ted Kennedy, one of the Senate's most doctrinaire liberals. Mr. Kerry's votes coincided with Mr. Kennedy's 100 percent of the time, confirming yet again their relationship as "the Massachusetts Twins." For Mr. Biden, it was 15 out of 16, producing a "Kennedy rating" of 94 percent. Mrs. Clinton agreed with Mr. Kennedy on 14 of the 16 votes (88 percent), and Mr. Feingold's votes matched Mr. Kennedy's 13 times (81 percent). Mr. Bayh, the most moderate of the five, voted with Mr. Kennedy 11 out of 16 times (69 percent). . . .