John P. Sears, a Republican political strategist who worked for Richard M. Nixon and Ronald Reagan and was fired by both, died on Thursday in Miami. He was 79. His son, James, confirmed the death. He said Mr. Sears had a heart attack. Mr. Sears was only 28 in 1968 when he served as deputy director of field operations for Nixon and helped him secure the Republican presidential nomination. He then worked briefly as deputy counsel in the White House. Within a year, he was fired. The firing removed Mr. Sears from the Watergate scandal, which led to Nixon’s resignation as president. Mr. Sears returned to politics in 1976 to manage Reagan’s bid for the Republican nomination. Mr. Sears helped run Reagan’s successful bid for the nomination in 1980. But he was fired during the New Hampshire primary just before the returns came in showing that Reagan had crushed George H.W. Bush. Mr. Sears had run afoul of Reagan’s California team, including Reagan's wife, Nancy, who found him overly controlling and viewed him as preventing Reagan from being himself. John Patrick Sears was born on July 3, 1940, in Syracuse, N.Y. His father, James Louis Sears, was a dairy farmer and banker. His mother, Helen Mary (Fitzgerald) Sears, was a teacher and guidance counselor. A smart student, he skipped two grades in high school and was 16 when he began college at Notre Dame. He earned a bachelor’s degree in chemistry there in 1960. He got a law degree at Georgetown in 1963. He married Carol Osborne in 1962, and they had three children. She died in 2011. In addition to his son James, he is survived by two daughters, Ellen Rayhill and Amy Nichols, and nine grandchildren, as well as two sisters, Mary Helen Sears and Eleanor Fala. Mr. Sears joined Nixon’s Manhattan law firm, Nixon, Mudge, Rose, Alexander, Guthrie & Mitchell. After he was fired from the Nixon White House, he returned to private practice, joining the Washington law firm Gadsby Hannah, where he worked from 1970 to 1976. He joined with a Democratic lawyer, Philip Baskin, to form the law firm Baskin and Sears. Mr. Sears left in the mid-1980s after critics made an issue of his having represented South Africa’s apartheid government. He later started his own small firm. Representing the tobacco companies, he helped facilitate the settlement between the tobacco industry and the states.