It's almost the end of this session of Congress, so we're looking back to see who were the most liberal members.
The DW-NOMINATE score was developed by Keith Poole and Howard Rosenthal as a way to determine where legislators voted in relation to each other.
By looking at how each legislator voted on every roll call vote compared to the member's peers, DW-NOMINATE is able to show how liberal or conservative a Congressman or Senator is.
Over the course of a session, they develop a score based on how they vote compared to their peers. By looking at hundreds of roll call votes and comparing them mathematically, the DW-NOMINATE process is able to figure out where each member sits politically compared to other members.
The closer to -1 a member's score is, the more liberal they are. The closer to 1 a member's score is, the more conservative they are. At zero, a member is considered very, very centrist.
On this list, the closer the score is to -1, the more liberal the member is.
Knowing this, Poole is able to rank them in order of partisan tilt based only on how they voted in a single session.
10. Rep. Keith Ellison (D-MN)
Score: -0.634
Votes: 773
Ellison, who co-chairs the Congressional Progressive Caucus, was the first Muslim ever to be elected to Congress. He also serves on the House Financial Services Committee.
9. Rep. Raul Grijalva (D-AZ)
Score: -0.639
Votes: 839
Grijalva, the other co-chair of the Congressional Progressive Caucus, has represented Arizona's 7th district for five terms, and serves on the Committee on Education and the Workforce and the Committee on Natural Resources.
8. Rep. Jan Schakowsky (D-IL)
Score: -0.647
Votes: 852
Schakowsky, a seven-term Congresswoman, is the Chief Deputy Whip for the House Democrats, as well as a member of the House Steering and Policy Committee and co-chair of the Seniors Task Force.
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