“Obama is a liberal, but he’s not the most liberal,” said Keith Poole, a University of California-San Diego professor who runs the site. By comparison, McCain is the eighth-most conservative. Ratings from Congressional Quarterly also provide a mixed picture.
In CQ’s calculation of party unity, which measures how often members vote with their party on bills where the parties split, Obama got a 97 percent rating last year. Ten Democrats had higher scores. On votes where Bush indicated his position, CQ found Obama supported the Republican president 40 percent of the time in 2007. That 40 percent rating put Obama in the middle of the pack for Democrats. In 2006, Obama voted with Bush 49 percent of the time.
McCain had the Senate’s highest presidential support score last year, 95 percent, but he missed more than half of the votes because he was campaigning. And McCain hasn’t always been such a strong backer of President Bush. He supported Bush 77 percent in 2005 and has averaged 89 percent since 2001.
National Journal relies largely on the judgment of its editors and reporters. They choose votes that they believe show ideological distinctions (they chose to include 99 of the 442 Senate votes last year) and they decide which side in the vote is liberal and which is conservative. Then they compute how often senators and House members vote each way.
“We’re trying to pick votes where some ideological differences are displayed and show how members of Congress line up relative to one another,” said Charles Green, editor of the magazine.
CQ takes a more empirical approach and calculates how often members vote with their party or the president.
“We don’t try to establish a litmus test or ideological label,” said John Cranford, CQ’s national editor. “What we’re looking for is something that more closely represents how members might characterize their vote, such as how often they vote with the president.”
The whole article is here.