Romney lost by moderate margins in Iowa, Minnesota, Wisconsin, Michigan, Ohio, and Pennsylvania. Among Great Lakes States, he won Indiana and lost by a lot in Illinois.
Hispanics and Asians aren't all that important in this swing region: in terms of voters, it's basically pre-1965 white and black America. And Romney just didn't appeal enough on manufacturing and jobs in that part of the country. How does the 2009 Auto Bailout sound as the key to the Electoral College in 2012? Perhaps the anti-unionized government workers war in Wisconsin didn't work out so well for Republicans?