Now that National Journal has released its annual round of vote rankings, I'm updating my chart detailing the voting patterns of the 32 Senators up for reelection in 2008 (one Senator, Republican Wayne Allard of Colorado, having already announced his intention to retire at the end of the 110th Congress). A few notes about the chart:

• Those Senators who appear in bold have been ranked by either the Cook Political Report (.pdf) or the Rothenberg Political Report as being vulnerable or potentially vulnerable this cycle.
• The National Journal composite score measures how the percentage of the Senate a particular member voted to the right or left of. A composite liberal score of 75 would mean that that particular Senator tended to vote to the left of 75 percent of his or her colleagues across all issues in 2006; likewise, a composite conservative score of 75 would mean that a particular Senator tended to vote to the right of 75 percent of his or her colleagues across all issues in 2006. For Republicans, I have listed the composite conservative score while for Democrats I have listed the composite liberal score.
• The other two ratings, party unity and presidential support, come from Congressional Quarterly. The first is a measure of the percentage of the time that a particular voted with his or her party when a majority of that party caucus voted in opposition to the majority of the other party caucus in 2006. The second measures the percentage of the time that a particular Senator supported the President's position on a particular vote before the chamber in 2006.

It's worth noting that because the National Journal rankings deal in percentiles rather than hard numbers, a particular Senator might appear more moderate than he or she deserves credit for. For instance, Norm Coleman's 53.8 conservative score would seem to put him not too far out of line with his Minnesota constituents, but a gander at his party unity and presidential support scores -- 77 and 88, respectively -- paints a different picture: one of a Senator too beholden to his party's leadership. Similarly, Susan Collins comes off well in the National Journal rankings with a score that actually places her in the left half of the Senate, but her party unity (66) and presidential support (79) scores indicates she's not quite the centrist maverick you might assume she is. This is not necessarily meant to be a knock on the National Journal rankings, because I definitely think they have their purpose (perhaps most importantly so that we can track a Senator's voting record over time). Still, it is worth keeping in mind that the National Journal rankings are not the be all and end all of vote rankings.

Below the fold: Democrats up for reelection in 2008.