The Short Version
The claim that Trump is the least popular president in U.S. history based on approval ratings is false. Gallup and academic records show Truman hit 22% approval (1952), Nixon 24% (1974), and Carter 28% (1979) — all significantly lower than Trump's recorded low of 29–34%. On career-average approval, Trump's ~40% is tied with Biden, not uniquely the lowest. No standard approval metric supports the "least popular in history" superlative.