… Pennsylvania alone would not have won the election for Mr. Romney. But if the national climate had been slightly better for him over all, he might have won Ohio and Florida. Winning Pennsylvania as well would have given Mr. Romney the Electoral College, even if he had lost Colorado, Virginia and the other swing states that Mr. Obama in fact carried.
There is one additional complication for Republicans in Pennsylvania, however: it has often been a close-but-not-quite state for them. They can find 48 percent of its vote pretty easily, but finding 50 percent is difficult; Mr. Romney was hardly the first Republican to make a late play for the state but fail to win it.
The reason has to do with another FiveThirtyEight concept, which we call “elasticity.” [cont.]
Nate Silver, FiveThirtyEight (NYT)