Since this thread is for ideal candidates, I'll include candidates who I don't think will run.
Illinois - Lisa Madigan (but I don't think she'll run)
Missouri - Not sure anymore. I think Nixon is damaged goods. Maybe Jason Kander?
New Hampshire - Either John Lynch (who I don't think will run) or Maggie Hassan (who I have doubts about)
North Carolina - Anthony Foxx? I think him, with Cooper clearly gunning for Governor.
Ohio - Tim Ryan or Richard Corday? I don't think either would beat Portman, though, unless the environment is putrid for Republicans.
Pennsylvania - Tough one. I think Kane is damaged, and she was supposed to be the Pennsylvania Democrats' star. Their bench isn't stellar, but maybe Shapiro? Rendell would be great, but I doubt he runs.
Wisconsin - Feingold or Kind. I'm sure there are others who could beat Johnson as well.
You don't think the democrats can make Ohio or North Carolina competitive even in a presidential year?