Hotline On Call

Oklahoma's Tom Coburn is the most conservative member of the Senate, while New Yorker Kirsten Gillibrand and Oregon's Jeff Merkley share the title of top liberals, according to National Journal's 2011 Congressional Vote Ratings.

Coburn jumped eight spots to snag the most conservative label this year, and it's Gillibrand's second consecutive appearance in the list of top ten most liberal members.

(PICTURES: Most Liberal Senators | Most Conservative Senators)

For the past three decades, National Journal has rated members of Congress based on selected roll-call votes from the previous year to create an ideological scale for Congress. This year, National Journal examined all 949 roll call votes in the House and each of the 235 cast by the Senate, pulling out those that demonstrate clear ideological gaps.

Many votes don't make the cut -- those that involve noncontroversial issues or that fall along regional lines, for instance. This year, 105 House votes and 97 Senate roll calls made the cut in our as economic, foreign or social policy categories.

After the jump, take a look at the full list of the ten most conservative and ten most liberal members of the Senate. And stay tuned to NationalJournal.com as we roll out the annual ratings.