Is absolutely the last thing Dems want. I guarantee new Dem ads where they show Romney-Ryan not only pushing old ladies off cliffs, they'll show them killing puppies with hammers. They're that awful. The leftist inclination is not to argue legitimate topics, it is to annihilate the opponent any way possible. The worse the smear, the better.
That's what they did with Sarah Palin last time around. The McCain campaign did not handle that very well. It remains to be seen how the Romney campaign will do, but Ryan has the advantage of having been under attack by the Dems for years and he will not be an easy target.