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

Kutler died Tuesday in hospice care in the Madison suburb of Fitchburg, according to his son, Andy Kutler.

Kutler taught for 32 years at the University of Wisconsin-Madison, retiring in 1996. 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.

Kutler used transcripts of the tapes to write the 1997 book "Abuse of Power." He also wrote "The Wars of Watergate."