This one totally passed me by:

Sen. Barack Obama, D-Ill., was the most liberal senator in 2007, according to National Journal's 27th annual vote ratings. The insurgent presidential candidate shifted further to the left last year in the run-up to the primaries, after ranking as the 16th- and 10th-most-liberal during his first two years in the Senate.

Sen. Hillary Rodham Clinton, D-N.Y., the other front-runner in the Democratic presidential race, also shifted to the left last year. She ranked as the 16th-most-liberal senator in the 2007 ratings, a computer-assisted analysis that used 99 key Senate votes, selected by NJ reporters and editors, to place every senator on a liberal-to-conservative scale in each of three issue categories. In 2006, Clinton was the 32nd-most-liberal senator.

,,,

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. On social issues, which include immigration, McCain received a conservative score of 59.

The National Journal also notes:

 As Obama and Clinton have wooed Democratic primary voters, both have emphasized their liberal policy positions. But neither has embraced the liberal label the way that the Republican presidential candidates have proudly stamped themselves as conservatives.

In Obama's first splash on the national stage, as keynote speaker at the 2004 Democratic National Convention, he disparaged ideological labels as weapons used by partisans who have little else to offer. "Even as we speak, there are those who are preparing to divide us, the spinmasters and negative-ad peddlers who embrace the politics of anything-goes," he said. "Well, I say to them tonight: There's not a liberal America and a conservative America -- there is the United States of America."

But there's a very liberal Obama.