According to
CNN:
Kerry's campaign also has outlined for Clinton other ways he can help rally voters and participate in the last two weeks of the presidential campaign, including visits to battleground states.
"There has been some discussion with the former president about things that will be great for him to do," said Kerry adviser Mike McCurry. "We're hoping that something will be able to come together."
The article mostly talks about an appearance in Penn. next week, but I think we need him mostly in three states: Arkansas, North Carolina and Virginia. Arkansas is obvious. Recent polling has shown the state to be fairly malleable, and within striking range of Clinton pushes hard. North Carolina and Virgina are closer, in my opinion, and Clinton's southern charm will do very well. Tennessee might be a good one to hit as well.
Clinton is a very potent solvent for the "Solid" South.