John Kerry was attacked because HE kept changing his stance. He was a joke of a candidate.
The worst they could say is that Republicans are able to accept disparate points of view within the party. And I don't see how that's an attack that would work, especially against someone like RG who has almost a larger-than-life image. But I guess we'll see how this all shakes out in the end.
Speculation is most of the fun!
It won't be as simple as that. The republican party will be divided and full of in-fighting. Remember, we'll have to fight in senate elections too. If we can't produce a united front, we'll be seen as disorganized and without a message. If the democrats get a stong nominee who pulls the party together, we'll get slaughtered.