Ben Nelson retires, nation mourn-celebrates

Ben Nelson announced today that he would not seek reelection, meaning that Nebraska might elect a Republican for Senate.

(A: Incumbents usually do better and races with two aspirants are more a toss-up; B: Nelson announced this now, leaving Democratic officials with less time to find a replacement; C: Nebraska isn't the most Democratic-friendly state.)

Now, there's not a lot to love about Nelson as a Democrat, so part of me is happy to see him go--but will his replacement be any better? Time for some postulates!

1. A guy who votes with you sometimes is better than a guy who never votes with you.
2. But optics matter, and a "Democratic supermajority" that can't do its job damages the Democratic brand. So a "Democratic supermajority" made up of Nelsons and Liebermans is a potential net-loss--they may vote with you sometimes, but make you look bad the rest of the time. 

Which is more important? Nelson's occasional votes in support of the Democratic agenda; or his damage to the Democratic Party as a whole by blocking Democratic bills while under the name of Democrat?