Mitt Romney has the lead regardless of who he picks. Currently, Obama is in panic mode as he can't keep his ratings up in the election or approval polls. He's creating executive orders to appease to special interest groups and sympathetics or tries to use an occasional threat of power (power he doesn't possess nor warrant in any legal capacity). If he can create a dictatorship by fooling people into believing that they already have one, then he will. That kind of desperation and insecurity reveals not only that he is out of touch with the desires and the expectations of mainstream America, but that his personal presidential agenda is in a free fall.
Mitt Romney can pick anyone he wants. Whoever he picks for VP will be a sound choice.