Watergate historian Stanley Kutler, who battled for and won the release of President Richard Nixon's secret tapes, has died.
Professor Kutler, 80, who had been in declining health, died in hospice care in the Madison suburb of Fitchburg, Wisconsin.
His son Andy said his father "just had a love and a passion for the United States Constitution" and considered the Watergate scandal that drove Nixon from office in 1974 "an affront".
"He wanted to make sure the whole story was heard," he said.
Prof Kutler taught for 32 years at the University of Wisconsin-Madison, retiring in 1996, and remained a professor emeritus. He wrote several books, including two on Nixon.
In 1992, Prof Kutler and Public Citizen, an advocacy group, sued the National Archives to force the release of thousands of hours of White House conversations recorded by Nixon's secret taping system. Prof Kutler won the gradual release of 3,700 hours worth of tapes in 1996.
After winning release of the Nixon tapes, Andy Kutler remembers his father going to the National Archives and listening to the scratchy "horrible audio recordings".
Prof Kutler used transcripts of the tapes to write his 1997 book, Abuse Of Power. He also wrote The Wars Of Watergate: The Last Crisis Of Richard Nixon.
In 2013 he said the most damning conversation was Nixon telling aides in August 1972 that the Watergate burglars "have to be paid" to keep them silent about the June 1972 break-in at Democratic offices in the Watergate complex.
"That cuts to the whole heart of the matter of obstruction of justice," he said.