From the introductory post:
In compiling the rankings for each chamber, ADA scored 20 votes from the second session of the 111th Congress on issues including health care reform, repeal of “Don’t Ask Don’t Tell”, unemployment compensation, and ratification of the New START nuclear weapons treaty. Since their first issuance in 1947, ADA scores have been relied upon by scholars, journalists, and the general public as the standard indicator of American political ideology.
Excerpt from the report:
ADA’s Congressional scorecard shows that the 111th Congress took a sharp rightward swing in the second year of the Obama Administration. In 2009, only one Senator (Republican Jim Bunning of Kentucky) earned an ADA “zero” by opposing the ADA position on every key vote. Last year, the number of Senate zeroes ballooned to 19 – nearly half of the Republican caucus. Conversely, 16 Senators in 2009 boasted a perfect ADA score of 100; in 2010, there were only five such Senate “heroes.” While not quite as dramatic, the shift in the House was also pronounced: in 2009, 75 zeroes and 98 heroes; in 2010, 90 zeroes and 48 heroes.
The ultra-conservatism of the House Republican caucus is striking. Of the roughly 178 Republican members (the number varied slightly through the year as vacancies occurred), only three voted as much as a third of the time with ADA. Only nine voted the ADA position over a fourth of the time, and only 13 House Republicans voted ADA’s way on as many as one-fifth of the tracked votes. Overall, the House Republicans scored 5%, while their Democratic colleagues received an 84%. The Senate party averages were 7% for Republicans and 88% for Democrats.
In conclusion: Damn that Obama for being unwilling to Reach Across The Aisle™.