The Baraqqi Coalition is well defined:
Baraq will never fall below about 40% baseline support. His 2012 plan is a three way split and a Clintonian plurality win.
But given the dynamism of the current crop of GOP leaders I think there's a good chance we can make significant inroads into the dead people demographic.
You assume that Barak will survive the primary challenge. He probably will. I can’t think of a sitting president that didn’t, but he could get mussed-up a bit. He might be the loser in a 3-way.