There's a pretty obvious "Texas sharpshooter" fallacy going on here. He does not claim that his formula predicted the events before they happened. He came up with a formula that explains things after the fact. I am particularly suspicious that at least according to the article, there is no weighting applied to any of the 13 factors; each is apparently equally significant. Note especially that he does have some fairly fuzzy categories in there, like significant scandal, charisma of both candidates, etc.
There are any number of simple factors one could come up with to predict the results of the last X elections. Start with:
1. All other things equal there is a strong tendency for the party in power to remain in power for 8 years and then turn over the White House to the party out of power.
2. Incumbent presidents always win re-election (provided they were originally elected) unless the economy goes into recession in the last year or so of their term, or they took office as the result of a major scandal.
3. If there is no incumbent president running, the party out of power will win unless their candidate is filmed riding around in a tank.
Explains every election since 1956. Eisenhower was an incumbent in 1956 with no recent recession. In 1960, there was no incumbent running and so the party out of power (Democrats and JFK) took over. LBJ wins on the 8 years of power rule with no recession. 1968 no incumbent, so turnover to the Republicans. 1972, incumbent wins. 1976, incumbent took office as the result of a major scandal, plus 8-year rule. 1980 incumbent loses due to late-term recession. 1984 incumbent wins. 1988, well, you do have the tank. 1992, recession plus pressure from the usual 8-year turnover. 1996 incumbent. 2000 8th year, 2004 incumbent 2008 8th year, 2012 incumbent, 2016 8th year.
ETA: Obviously the tank bit is a joke, but it would not be too hard to come up with some sort of oddball but reasonable criterion that explains 1988 but does not apply to the other years.
