This week National Journal released their annual vote rankings, which measure where within the Senate or House a particular member of Congress lies. As the editors explain in the methodology section, "The liberal percentile score means that the member voted more liberal than that percentage of his or her colleagues in that issue area in 2006."

Below I have recreated the table containing both scores and rankings for each of the five Democratic presidential candidates currently serving in Congress. I have ordered the candidates in the Senate from most liberal to least on the composite score and separated the lone House member in the race, Dennis Kucinich, to make clear that this is more of an apples-to-oranges comparison between chambers than an apples-to-apples one.

As you can see from the chart, Barack Obama is across the board the most liberal candidate in the race who is currently serving in the Senate, though Chris Dodd is not far behind him. Dennis Kucinich is slightly more liberal in relation to his chamber than is Obama, but nearly a quarter of his party's caucus in the chamber was more liberal than him in 2006, according to National Journal (while exactly one-fifth of Senate Democrats were more liberal than Obama in 2006). Joe Biden is in the middle of the pack of Senate Democrats, or slightly to the right of the median, and Hillary Clinton hails from the most conservative third of the party caucus in the chamber.

On economic issues, Obama and Biden are tied with others for being the most liberal within the chamber, while Dodd is not too far behind. Clinton is in the most conservative fifth of the caucus on economic issues while Kucinich is about exactly in the middle of the House Democratic caucus.

On social issues, Kucinich is near the top of the House Democrats in terms of liberal score, while in the Senate Dodd is near the top, as well. Clinton just comes in among the most liberal third of her caucus on social issues, while Obama and Biden are near the middle of the caucus, with Obama slightly to the left of the median and Biden slightly to the right.

None of the candidates in the race is terribly liberal on foreign policy, though both Kucinich and Obama are among the most liberal quarter of their respective party caucuses. Dodd is near the middle of Senate Democrats on foreign policy while both Biden and Clinton are in the most conservative quarter of their party's caucus on the issue.

Now the National Journal vote rankings are not the be all and end all of vote rankings and, what's more, judging a member of Congress' voting record in a single year is not necessarily the best way of judging how liberal or conservative he or she is -- or, for that matter, how liberal of a President he or she may be. That said, they do paint an interesting picture and will undoubtedly be used by campaigns and outside interest groups to portray candidates as too liberal or too moderate or just liberal enough or just moderate enough, and as such are worth taking a gander at.

Also, later on this weekend I will update my chart of the vote rankings of the Senators up for reelection in 2008.