Lee Atwater, former chairman of the Republican National Committee and a major architect of George Bush's Presidential election victory in 1988, died at George Washington University Hospital. He was 40 years old. He died after a yearlong fight against a brain tumor that struck him at the peak of his political success and power. Harvey LeRoy Atwater was universally as Lee. He was only 37 years old when Mr. Bush named him chairman of the Republican National Committee as a reward for managing the 1988 campaign. Mr. Atwater first came to national attention at the age of 29 when he helped Ronald Reagan win the 1980 Republican Presidential nomination as the campaign's political coordinator. He graduated from Newberry College in Newberry, S.C., and earned a master's degree in communications from the University of South Carolina. Mr. Atwater and his wife had three daughters, Sarah Lee, Ashley Page and Sally Theodosia, who was born after Mr. Atwater's tumor was discovered. Other survivors include his parents, of Columbia, and a sister, Ann Atwater King, of Charleston, S.C.