The only reason? There isn't that much difference between Santorum and Casey then?
I'm a third party guy: certainly no GOP cheerleader. But anyone who seriously believes that Casey, a democrat, is going to step up on the war on terror and illegal immigration is out of their mind. I know WHAT HE SAID, look at what they do.
"The only reason you need". Sufficient but not necessary, as the math people would say.