U.S. Republican presidents of the past 50 years had an average IQ of 115.5, with President Nixon having the highest IQ, at 155. President G. W. Bush was rated the lowest of all the Republicans with an IQ of 91.

Democrat presidents had IQs with an average of 156, with President Clinton having the highest IQ, at 182. President Lyndon B. Johnson was rated the lowest of all the Democrats with an IQ of 126.

(Lovenstein Institute think tank)