As we noted here yesterday, Pennsylvania is now in play. Money in the form of TV ads is gushing into this state.

Now, here comes Mitt. This Sunday, Romney will be campaigning in suburban Philadelphia. For non-Pennsylvanians, there are four suburban counties that ring Philadelphia. For a Republican to win Pennsylvania they are a must-win. The thought had been that so many of these Republicans had voted for Obama in 2008 that Romney had no chance to win them back.

Wrong. Big time. The enthusiasm for Romney rises here as the results of Obamanomics have hit home. Former Governor Ed Rendell, a Democrat, has now said there is the possibility of a “startling upset” in Pennsylvania.

So come Sunday, with campaign time for Romney now his most valuable asset, he will be in those vote rich GOP suburbs.

There is only one reason to do that — and the potential of a “startling upset” is that reason.