Reagan won against a severely politically wounded President in a much Whiter America.
Is it just a coincidence that Kennedy, Clinton, and Obama are a combined 5 - 0 in Presidential contests and almost undefeated in Presidential debates.
The high stakes salesmanship of Presidential contests will usually require a great deal of sustained energy, aggression, and very strong rhetorical skill. These are far better served by youth than old age.
I'd like to see Cruz or Rubio against that tired looking Hilary Clinton.