LBJ's 1964 victory was because of JFK's assassination less than a year before - not because LBJ was such a remarkable president.
WJC’s 1968 victory was, to a significant degree, a response to the Republicans 1994 victories. The American public likes a divided government where no one political party controls everything.
BHOI’s 2009 victory was the result of many things. The most important was the concerted effort by the national media to get a know nothing, done nothing, snake oil salesman president.
BTW the real meaning of “margin of error” is the ability of the survey to repeat the results. It is an internal check of the poll’s process NOT the accuracy of the poll.
Dude, don't drink and time-travel. ;)
/johnny