He could have yes. Some things would have to change obviously. Perhaps if he sharpens his focus in the senate even in the mid 70's that could be a start. Get a handle on his drinking. Avoid that disaster of an interview, or at the very least have a statement ready and be prepared for that question instead of asking for softballs.
Determination is key. I've long thought that Teddy didn't want the presidency, or didn't really want to try, and was only doing so because of the fact that he was a Kennedy. So, if we see a more determined Teddy, a fighting ready Teddy, coupled with the legend of the Kennedy's, we could very well see the next president Kennedy.