i'm sure there all all sorts of "plan B's" going on for now and for 2016.
If the convention is brokered, you have romey 'agreeing' to put santorum on ticket as veep... or vice versa...
Or RP has enough delegates that refuse to choose mittens, and maybe they just go and select Rand

Or maybe RP's biggest goal is paving the way for a Mittens loss, ensuring a good chance Rand Paul is the frontrunner for 2016.