Patrick Caddell, the political pollster who helped send an obscure peanut farmer named Jimmy Carter to the White House, later became disillusioned with fellow Democrats and finally veered right to advise supporters of Donald J. Trump, died on Saturday February 16 2019 in Charleston, S.C. He was 68. His death, from complications of a stroke, was confirmed by a colleague, Prof. Kendra Stewart of the College of Charleston. While Mr. Caddell was considered instrumental in Mr. Carter’s victory in 1976, he also shared the blame for limiting him to a single term. By the late 1980s, Mr. Caddell had become disaffected with the Democratic Party. In 2016, he became a frequent commentator on Fox News and advised Stephen K. Bannon, who became President Trump’s chief White House strategist, and Robert Mercer, a computer mogul and contributor to the Trump campaign. Patrick Hayward Caddell was born on May 19, 1950, in Rock Hill, S.C. His mother was Janie (Burns) Caddell. His father, Newton P. Caddell, was a Coast Guard chief warrant officer. He was still an undergraduate at Harvard, where he earned a bachelor’s degree in political science in 1972 and started a thesis on “the changing South,” when he started polling professionally for Senator George S. McGovern’s fledgling presidential primary operation. He established his own firm, Cambridge Survey Research, to conduct political campaigns. Although he spun off another company, Cambridge Reports, to advise corporate clients. Mr. Caddell is survived by a daughter, Heidi Caddell Eichelberger; a brother, Daniel; a sister, Patricia Roberts; and three grandchildren.