Ιf Romney had any class and wanted to show to Santorum that he respects him then he shouldn't contest Pennsylvania.
But we are talking about Romney here, a man who is unanimously hated be all the other 2008 and 2012 candidates.
My friend, Romney has, by many accounts, approximately 40% support in PA, and that will likely be growing. Why would you want to deprive these people of having their opportunity to support Romney in the primary, while Santorum has been mean mouthing him for months now?
Santorum's the one who should not be contesting PA, by announcing his withdrawal from the race.
This may happen if there is some validity to the statement from Eraserhead that he expects Santorum to be withdrawing next week, based on what he's been hearing. I do not know his sources.