He can't win the GOP nomination because he's not extreme like the other guys and that's what the base wants right now. Doesn't matter what kind of campaign he would run.
3% in NV isn't only extremists
5% in GA isn't only extremists
6% in FLisn't only extremists
6% in LA isn't only extremists
3% in AR isn't only extremists
5% in MN isn't only extremists
Some of these aren't even major conservative states with a bunch having gone to Romney.
The polls have always shown Sanders beating all of them. What does that tell you?