In making this map, I though less about the 2012 candidates and more about where each of the three parties would have appeal. I don't see any of them being particularly appealing in the "rust-belt" region, because the Greens, Libertarians, and Constitutionists exist on largely non-economic planks (or, in the case of Libertarians, it is not their economic philosophy which motivates most of their voting base).
Green Party: 250Libertarian Party: 156Constitution Party: 132The Constitutionists only compete in the south, plains states, and mountain west. That means in traditionally Democratic states, the Greens win the leftist vote, and Libertarians the right. Of course, the election goes to the house, and it's anybody's guess who the house selects.