40. James Buchanan – 139.6
James Buchanan, the 15th president, held office for a single term from 1857, a period fraught with escalating tensions leading up to the Civil War. As anticipated, his presidency was marked by the mounting conflicts of the era. Notably, Buchanan possessed exceptional qualities as a debater and displayed a deep understanding of the law. The White House website aptly describes him as “gifted as a debater and learned in the law.” These attributes are further reflected in his above-average IQ, placing him within the top two percent of scores. Buchanan’s intellectual prowess undoubtedly played a role in his ability to navigate the challenging political landscape of his time.