With an election with an odd map, Snowe wins the election, but Landrieu becomes VP. Jersey is the close state that decides the election, while West Virginia narrowly eludes Collins of the VP spot
I think you underestimate Nelson/Landrieu. Southerners only vote Republican when they do for social issues, not economics. You'd be running two socially conservative economic liberals against two social moderate economic conservatives
Democrats win every state in the South with that kind of ticket, save maybe Texas