After leading a much-publicized investigation into organized crime in the early 1950s, he twice sought his party's nomination for President of the United States. In 1956, he was selected by the Democratic National Convention to be the running mate of presidential nominee Adlai Stevenson. He still held his U.S. Senate seat after the Stevenson–Kefauver ticket lost to the Eisenhower–Nixon ticket. Kefauver was named chair of the U.S. Senate Antitrust and Monopoly Subcommittee in 1957 and served as its chairman until his death.