Chuck Wielgus, who as the top official in American swimming was credited with doing more than anyone to make it the nation’s premier Summer Olympics sport, but who was later scarred by his response to accusations of sexual abuse by coaches, died on Sunday in Colorado Springs. He was 67.

A spokesman for U.S.A. Swimming, the organization Mr. Wielgus ran as executive director, said the cause was complications of colon cancer.

As head of U.S.A. Swimming from 1997 until his death, Mr. Wielgus (pronounced WILL-gus) was the longest-serving leader of any United States Olympic organization. His swimmers brought home a third of United States medals in the last five Summer Olympic Games, many won by Michael Phelps, the most decorated Olympian ever.

Along the way Mr. Wielgus expanded his organization’s revenue, membership and fan base exponentially.