Just because he didn't win them (again, consider his opponent) doesn't mean he doesn't have sway with them. McCain-Santorum vs. Obama-Biden would be nothing like Santorum vs. Casey. Obama-Biden doesn't have the type of appeal that the Casey name has with white, blue collar, Catholic voters.
While I disagree that this voting block we've argued over is as organized as you've made them out to be, when you lose an election by 17+ points, it stands to reason you've alienated just about every voting block there is. Don't get me wrong; I wouldn't have expected Rick to beat Casey but I would've figured he'd come closer than 17+points.
I think Santorum would be disaster for McCain amongst these voters.