“But, I really dont give this plan much of a chance of success.”
I agree with your reasons, but I still think Harry Reid will be a factor. How can they denigrate Romney without denigrating Reid? But again, it’s Romney’s job to call them on this.
They've had a lot of time to game this out. Their intention is to create an overall negative background buzz against Mormonism as a whole, so that any time Romney's Mormon beliefs are mentioned in any other context, the audience will immediately reflect back on the last thing they saw or heard about Mormonism -- which will be negative.
It's a subtle game they are playing, and it will work in some cases.
My personal belief is that Americans are smart enough to see through their game and are not going to be sufficiently swayed by the hit pieces to allow it to influence their vote. But then, I also remember the immortal words of H. L. Mencken:
Nobody ever went broke underestimating the intelligence of the American public.
So I could be wrong.