Stanley Kutler, the Watergate historian who famously sued for the release of President Richard Nixon's secret tapes, died Tuesday in Madison, Wisc. He was 80 years old. Kutler had been in declining health in hospice care, according to his son Andy Kutler. The historian authored several books and taught for 32 years at the University of Wisconsin-Madison, where he remained a professor emeritus after retiring in 1996. In 1992, Kutler and advocacy group Public Citizen sued the National Archives to release Nixon's secret tapes of White House conversations. He won the eventual release of all 3,700 hours in 1996, which informed his book Abuse of Power, and later The Wars of Watergate: The Last Crisis of Richard Nixon.