Obama took care to irradiate the swing states with his negative attacks on Romney. When the voters in those states saw that Mitt was not a Halloween monster but a pretty nice and reasonable guy, his negative stopped working and the states started falling to Romney.
But in Pennsylvania, Wisconsin, Minnesota, and Michigan, the negatives on Romney never ran. The only Romney they saw in these states was the very presentable and attractive one who showed up in the debates. So there was no obstacle to hold them back from voting for Mitt.
Obama’s static dependence on the swing states to constitute a firewall backfired. The firewall became like the French Maginot Line of 1940, easily outflanked.
And, in this final week, Romney’s campaign and its allied groups are spending $11 million on Pennsylvania ads as opposed to only $2 million for Obama.