CHICAGO — Rich Williamson, a former aide to three Republican presidents who lost a widely watched race for the United States Senate in 1992 to Carol Moseley Braun, the first black woman in the Senate, died here on Sunday. He was 64.
Illinois Republican Party officials announced his death. The cause was complications from a cerebral hemorrhage, a family spokesman said.
Mr. Williamson, a lawyer and a foreign policy scholar and author, was appointed to foreign policy and diplomatic roles under Presidents Ronald Reagan, George Bush and George W. Bush. He was a senior adviser to the presidential campaigns of John McCain and Mitt Romney.
He became widely known after reluctantly agreeing to seek the Republican senatorial nomination in 1992, believing he would be challenging the incumbent Democrat, Alan Dixon. But Ms. Braun defeated Mr. Dixon in a three-way primary contest.
Ms. Braun, a Democrat, defeated Mr. Williamson in the general election with 55 percent of the vote.
Mr. Williamson was a former ambassador to the United Nations Commission on Human Rights and in 2008 was appointed by President Bush to serve as special envoy to Sudan to work on ending genocide there.
He continued to work on the issue after Mr. Bush left office. In July, he and the former Secretary of State Madeleine K. Albright issued a report on genocide prevention. “As we know from our experience in government service, once the body counts begin to mount, our options for responding immediately become far less palatable politically,” they wrote.
He was chairman of the Illinios Republican Party from 1999 to 2001 and since 2010 had been the state’s Republican National Committeeman.
Richard Salisbury Williamson was born on May 9, 1949, in Evanston, Ill. He graduated from Princeton and the University of Virginia School of Law and was a senior fellow of the Brookings Institution in Washington.
Information about his survivors was not available.