Sure there is a Catholic vote, the catholic denomination has always voted democrat (with 4 or 5 exceptions) and still does, and always will, (with hopefully a couple of more exceptions) it is how that church denomination votes.
I think today-—not in the past-—white Catholics are now voting pretty much along the same lines as the general white population. I believe race is now a much bigger factor than religious affiliation. Religion IS a factor though. Active church goers tend to vote more Republican than secular voters this applies to all denominations.