IQ is still only a so-so predictor of success for a President, it doesn’t judge a President’s learning method, ability to rigorously fact check sources, fortitude, mental flexibility, leadership, teambuilding skills, bureaucratic support, ect…:
In terms of brute brainpower, the smartest postwar presidents were Richard Nixon, a Duke Law School graduate with a reported IQ of 143; Jimmy Carter, who graduated in the top 10 percent of his Naval Academy class; and Rhodes scholar Bill Clinton, a graduate of Georgetown University and Yale Law School. Deeply flawed presidencies all, despite their potential.
In contrast, take high school graduate Harry Truman — railroad worker, clerk, bookkeeper, farmer, road inspector and small-town postmaster — or Ronald Reagan, sports announcer and B-list actor with mediocre college credentials.
Despite their intellectual limitations, both achieved substantial political success as president. And, to press home the point, there is Franklin D. Roosevelt, a top-tier president in rankings of historical greatness, whom the late Supreme Court justice Oliver Wendell Holmes branded “a second-rate intellect but a first-class temperament.”