Watergate historian Stanley Kutler, who successfully fought for the release of President Richard Nixon’s secret tapes, died on Tuesday in Wisconsin. He was 80.

Kutler, who had been in declining health, died in hospice care in the Madison suburb of Fitchburg, according to his son, Andy Kutler.

Andy Kutler 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 to the Constitution.”

“He wanted to make sure the whole story was heard,” Andy Kutler said.

Stanley Kutler taught for 32 years at the University of Wisconsin-Madison, retiring in 1996, and remained a professor emeritus. He was the author of several books, including two on Nixon.

In 1992, 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. 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.”

Stanley 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.”