Someone who lives like a pagan can be expected to vote like a pagan, whether or not they call themselves a "Catholic". That's not the bishops' fault, nor is it the fault of real Catholics.
You're right that the concept of a "[self-identified] Catholic vote" is meaningless.
What IS the Bishops' fault is their support of state-funded healthcare. The only reason they don't now support Obamacare is the abortion provisions.
When the Bishops speak out in favor of Gov't intervention it follows that the catholic rank and file will vote for it.
We can play this game with Evangelical votes and we will get up into the high 80's.
You're right that the concept of a "[self-identified] Catholic vote" is meaningless.
When looking at this group we should be talking about married status, gender, ethnicity, income.
I don't know what your church will do about all the schools and hospitals that are now mandated to provide contraception and abortificents. If your church leaders follow through and begin closing these institutions it will create all kinds of problems for a lot of people. If they don't how much credibility will they have left.