After Barack Obama fumbled his running mate selection in both choice and process by selecting Joe Biden, John McCain has a wide-open field for his choice of VP candidates. About the only limitation he has is to refrain from choosing another Senator.  McCain needs someone who can help address any weaknesses and who can add some serious outsider credentials to the ticket.  Plenty of potential picks can help McCain, including governors Tim Pawlenty, Sarah Palin, and even perhaps the young Matt Blunt of Missouri.

Mitt Romney, a former Governor, may be best positioned of all, though, on the economy.  If Romney gets selected for McCain’s running mate, he will be the only one of the four principals who has actually run a business, and run it successfully.  He knows more about economic policy in both academic and practical terms than any of them, and hits Barack Obama in his key strength among voters.

Romney (and Pawlenty and Blunt) also have another quality that Joe Biden lacks: potential to deliver battleground states.  Speculation about Michigan appears to have a solid basis in fact.  In May, Survey USA tested a McCain/Romney ticket against several different iterations of an Obama ticket.  Surprisingly, it beat every single possibility, but was especially strong against an Obama/Biden ticket:

• vs Obama/Biden: +18
• vs Obama/Clinton: +5
• vs Obama/Gore: +5
• vs Obama/(John) Edwards: +3

A McCain/Romney ticket slightly edges Obama/Biden among women and gets a 35-point advantage among men.  Interestingly, it gets 28% of the black vote, too.

Pawlenty and Blunt can help deliver battleground states, too, and Carly Fiorina and Meg Whitman can strengthen McCain on economic policy.  Mitt Romney can do both and has background in both public and private sector leadership that none of the other potential candidates have.  Moreover, Romney has proven himself an excellent debater in the kind of format used over the past year and will have little problem matching up against Biden next month in the one televised debate.

The other candidates have their strengths as well, and the choice of Biden leaves McCain with the happy burden of many options.  Romney appears to have the strongest credentials.