Sanford and Romney would be the strongest candidates. They both a bring strong economic background, which I believe is McCain weakest link.
Romney would also take Michigan away from the dems and bring in some votes in the N.E. region. Romney’s economic strength would also play well in Ohio and Penn whose economies are not doing so hot right now.
Sanford is well respected in the south. He would strengthen McCain in the south immensely. He would help with Florida and pull in many southern swing voters.
I think the gov of Louisiana would be a poor choice. One, he’s very young. Two, he’s about as experienced as a governor, as Obama is a Senator. Three, I don’t know how many votes outside of Louisiana he would bring for the ticket.
As I have pointed out to Owen, I have seen little evidence to suggest that Romney would be all that helpful in Michigan. In the most recent statewide poll in Michigan, McCain has inched ahead of Obama. McCain may very well carry Michigan on his own merits.
The only state in play in the New England is New Hampshire. It was Romney's loss in New Hampshire combined with his poor showing in Iowa which made most political analysts realize that Mitt Romney was a weak candidate. McCain has a very good chance of carrying NH by himself.
I strongly doubt that anyone is going to pay a lot of attention to what the VP candidate has to say about the economy.
On the purely EV calculus, the one person at Sedona who could be the big player is Tom Ridge. He likely delivers Pennsylvania's EV and could help with Ohio. (I am opposed to such a move due to Ridge's politics but the guy is still real popular in Pennsylvania.)
Sanford would be a very safe choice. He would strenghten McCain's standing with conservatives without undermining his appeal to independents. If McCain believes that Obama will be exposed during the campaign as the lightweight that he is, I could see McCain pickinng Sanford confident that enough swing states will come his way that 270 EVs are assured.