They would suggest it may signal that Romney is giving up on Ohio (and maybe other states) and is pinning his hopes on a real long shot, PA. That would be sort of desperate if that's what's going on. Or it could be that he feels his chances in PA are at least as strong as his chances in OH and he wants a shot to take one or both of the two. That's strategy, not desperation. Which is it? Probably we'll find out on election day.
I see it as desperation. If he doesn’t need PA to win, why come here? The only reason to leave OH is if it’s lost. Even if he was ahead in OH, he should stay there just to be certain, rather than dump money into a potential black hole in PA. How would he explain wasting money in PA if he lost it and also lost OH by a tiny margin?
If OH is lost, the best way to make up for OH is with CO, WI and NH. McCain/Palin campaigned their butts off in PA and had a huge loss. And no Republican’s won here since 1988. WI has a worse track record, but Paul Ryan and Scott Walker are good cards to play.
Romney could also go for CO, NH, NV and IA instead of PA, OH or WI. NV and IA have voted for the Republican Prez as recently as 2004. And CO and NH have been polling well for Romney.