Here is a graph I made using the estimates of Presidential IQ provided by an article published in Political Psychology by Dean Keith Simonton.
Presidential IQ, Openness, Intellectual Brilliance, and Leadership: Estimates and Correlations for 42 U.S. Chief Executives
Individual differences in intelligence are consistently associated with leader performance, including the assessed performance of presidents of the United States. Given this empirical significance, IQ scores were estimated for all 42 chief executives from George Washington to G. W. Bush. The scores were obtained by applying missing-values estimation methods (expectation-maximization) to published assessments of (a) IQ (Cox, 1926; n = 8), (b) Intellectual Brilliance (Simonton, 1986c; n = 39), and (c) Openness to Experience (Rubenzer & Faschingbauer, 2004; n = 32). The resulting scores were then shown to correlate with evaluations of presidential leadership performance. The implications for George W. Bush and his presidency were then discussed.
I have also included normal distribution curves for the IQ of the general population and presidential population for comparison. (Forgive the prehistoric formatting, I'm using an older version of excel on a different computer for this one.)