This is a problem. I don't see how Walker can win without Wisconsin.
Perhaps Bush is a better candidate after all. He can win Florida and strongly contest Virginia.
Every Republican candidate has some serious weakness. Not one has shown an ability to breach the Blue (Atlas red) firewall. Making one or two of the swing states of 2008 or 2012 shaky just won't be enough.
I can almost predict the ad campaign against Jeb: "Like brother, like brother". Republicans may have no problem with another President like George W. Bush... but just about everyone else will. Jeb might be better than his brother, but that is a very low bar.
The luster is off Christie.
Paul Ryan has never won a statewide race, including winning Wisconsin for Romney/Ryan in 2012. If he has no experience running a statewide race, what says that he could run a national race competently?
Rand Paul gets much support because his father was a dyed-in-the-wool libertarian... but the younger Paul is much more authoritarian on non-economic issues. That will turn off anyone who could possibly vote Democratic for the President.
Huckabee is best described as a regional candidate. He wins the southeastern sector of the US (except for Florida and Virginia) and states that never, ever, ever vote Democratic for President. That's far from good enough.
Santorum, Perry, and Rubio are just too dumb to be President.