He defeated Thomas E. Dewey. Truman's victory is considered to be one of America's biggest election upsets, with virtually every public opinion poll indicating Truman would be defeated. Suprisingly, Truman, a democrat, obtained 303 electoral votes compare to Dewey's 189. Truman won the popular vote by 49. 6 % compared to Dewey's 45.1%. while Thurmond, the second runner-up, drew the votes of only 2.4 percent of the public.