The thing is, Cruz is great and thankfully, he's no Goldwater, who did himself in and who was fighting against the ghost of an assassinated JFK. Neither of which Cruz will face.
All true. There's little danger of the voting public perceiving Cruz as Goldwater.
But the issue you've raised -- and it's an important one -- is how the GOP-e would react to his candidacy. They could still perceive him as Goldwater. They're dense enough. And scared enough.
In any event, the GOP-e are the biggest obstacle to a Cruz candidacy. The primaries will be tougher than the general.