Bill Diamond, a longtime lawmaker from Windham who served for years as Maine’s secretary of state and who more recently had become a vocal critic of the state’s child protective system, died Sunday.

Sen. Bill Diamond, D-Windham, speaks in August 2018 at the Maine State House in Augusta. Diamond died Sunday at age 80. (Joe Phelan/Staff Photographer)

He was 80.

“Bill Diamond was a dedicated public servant and leader, an incredibly compassionate and kind person, and a wonderful friend,” Maine U.S. Sen. Susan Collins said in a statement. “He was a tremendous advocate for the safety and well-being of Maine’s children through his many years as an educator and legislator but especially as the founder of Walk a Mile in Their Shoes.”

Diamond’s death was announced Monday by Walk a Mile in Their Shoes, the child advocacy nonprofit organization he helped found two years ago. No cause of death was given, although a statement last week on the organization’s Facebook page said Diamond was “stepping back from day-to-day activities for a period of time due to health reasons.”

“Senator Bill Diamond devoted his life to serving others,” Monday’s statement read. “His commitment to protecting Maine’s children began long before Walk a Mile in Their Shoes and continued throughout his lifetime.

“Bill gave his voice to children and families too often left without one. When systems failed, he demanded accountability. He challenged an entire community to stand up for those who could not stand up for themselves. Together we have.”

Then-state Senate President Libby Mitchell, D-Vassalboro, Sen. Philip Bartlett, D-Gorham, and Sen. Bill Diamond, D-Windham, right, laugh with Rep. John Martin, D-Eagle Lake, second from right, in April 2010. (Andy Molloy/Staff Photographer)

Diamond, a Democrat, was first elected as a member of the Maine House of Representatives in 1976 and served three terms there. He also had three different stints in the Maine Senate, from 1982-1986, from 2004-2012 and from 2014-2022. In between, he spent eight years as secretary of state from 1989 through 1997, mostly under Republican Gov. John McKernan.

Away from the State House, Diamond was an educator in the Windham and Raymond school systems for nearly two decades and spent time as superintendent of the Elan School, a controversial boarding school in Poland that has been closed since 2011.

Rick Bennett, a longtime Republican state senator who served with Diamond, said in a written statement he was saddened to learn of his passing.

“Bill dedicated decades of his life to public service, always guided by humility, integrity and an unwavering commitment to the people of Maine,” said Bennett, who this year unenrolled from the Republican Party and is now running for governor as an independent. “His tireless advocacy for children, particularly his work to hold the state accountable for its child welfare system, forced real improvements and almost certainly saved lives.”

Sen. Jeff Timberlake, R-Turner, called Diamond “one of the greatest.”

“Bill has been a true friend, and a real man, (and) has taught me more about the legislature and how to get things done than anybody else I know,” Timberlake said in a social media post Monday. “Rest in peace my friend God knows you’ve earned it.

In 2023, Diamond founded the organization Walk a Mile in Their Shoes with $25,000 of his own money to draw attention to high-profile child abuse deaths across the state and to advocate for reforms.