That seems a very odd thing to say this far out. Especially given the history of unpredictability in primaries.
Not for Republicans. You're thinking of the Democrats.
It's especially seems odd to think that Romney is the only viable candidate. The only reason he even has a chance is the popular belief that he would be most likely to defeat Obama, and how desperate and urgent that goal is to so many Republicans.
I see him as the only candidate the Republicans would nominate who isn't a nut. If you want to beat Obama, you will need someone at least as moderate as Romney.
Put Palin or Bachman or Paul in there, or any tea party extremist. Obama would LOVE that.