I don't think people have a problem with Nelson's conservatism per se (you don't see them grumbling about Pryor or Landrieu) but rather his eagerness to screw his party at every chance he got. And his retirement is another one of them.
If he really cared about the Democrats retaining the Senate then the least he could do would be to dissuade them from spending 1 million dollars in ads propping him up while he was considering retirement.
I didn't particularly dislike Nelson and he would be preferable to any successor. Of course a Dem senator from Nebraska has a different role to play and he gets a lot of leeway. What was galling was his many unforced errors. He seemed to pick the wrong battles with the national Dems when the right strategy would have been just to keep his mouth shut on them or to pick other battles where he could prove his independence in line with what his conservative voters wanted and not be so blatant about supporting a few donors.
