It's always hard to tell, IMHO Ryan shores up the base, he'll bring in a lot of TEA and libertarians too who are soft on Romney, but that's mostly enthusiasm as opposed to raw vote gain. I don't really consider Wisconsin in play but it's note entirely out of play either and Ryan will help there, at a minimum by forcing Obama to treat it as in play. He'll also cut into the Catholic vote, and he's counter-intuitive polling high among seniors in terms of favoribility, kinda counter-intuitive. As a whole? I really don't know. Anyone who isn't just an awful choice adds to Romney's numbers right now, nobody will not vote for Romney over Ryan who was already with Romney, but some on the fence will shift to Romney, that would have happened with any reasonable VP choice.