"There has been very weak support from conservatives for Romney for months now, but faced with the prospect of a pro-choice vice president, Romney's numbers improved," says an adviser to the campaign with ties to Romney. "Pawlenty's and Jindal's numbers didn't improve as much."
The problem for Romney: both Pawlenty's and Jindal's support among conservatives was far better than Romney's before the option of a pro-choice nominee came into play.
In fact, both Pawlenty and Jindal actually help a McCain ticket win states, whereas Romney's numbers continue to weaken the ticket nationally.