The list you posted of Senators up for re-election shows a couple of seats that are up, but the individuals listed as being in the seats are either dead or retiring. Max Baucus in Montana is retiring from his seat. And Lautenberg of New Jersey died while in office (Christie picked his temporary replacement).
Thanks. I did revise that list late last night, and corrected it on the basis of help from FReepers.
Hopefully more Democratas will be resigning soon - - - .