It seems to me that their could be no possible failure to kill JFK in Texas on 11-22-63. There had to be a back-up plan, or several. There would be no way to guarantee that things would go as smoothly as they did that day. It seems that back-up plans would have had to have gone from the simple sniper attack, to a more reckless follow-up, to as far as a widespread bloody coup, with contingencies for the spread of resistance nationwide.
I have not seen this topic covered elsewhere, and I wrot