The important thing would be for the Republicans to keep the pipeline full of bills, forcing the Senate Democrats to say "No", or forcing Obama to veto bills.
Maybe. But if the dems hold the Senate the media will portray it as a huge victory for Obama. It’s worth it to get rid of folks like Boxer and Reid. Can you imagine the looks on the faces of the media if they have to report Feingold losing, or Murray?
Also, keep in mind that regardless of what the total ends up being, there’ll be a bunch of dems up in 2012 who will become effective Republicans. Nelson in NE, Conrad in ND, Webb in VA, Tester in MT, McCaskill in MO, Brown in OH, Casey in PA, Nelson in FL, even Feinstein, Stabenow and Cantwell(especially if Boxer and Murray lose). So even if the dems win up with say 48, there’ll really be less than 40 dems who will be committed to the Obama agenda.