Wisconsin has some rust belt-like areas, though it's not purely a rust belt state. It clearly has quite a bit of regional variety. I think Democrats just have to realize that they can't take the state for granted, and do have to win at least a little more than just Milwaukee and Madison (though Clinton would've scraped by with higher turnout in Milwaukee.) While Obama won the state easily both times, it's not like he ignored it.
THIS. Obama was in Wisconsin in both 08 and 12 when it was clear he was going to win both times. He showed up, that mattered.