MASSACHUSETTS — Former New Mexico Gov. Bill Richardson, a longtime fixture of Democratic politics with turns as Energy Secretary and United Nations ambassador under the Clinton administration, died on Friday, the Richardson Center for Global Engagement said in a statement. He was 75.

Richardson died in his sleep at his summer home in Massachusetts.

“He lived his entire life in the service of others — including both his time in government and his subsequent career helping to free people held hostage or wrongfully detained abroad.

“There was no person that Governor Richardson would not speak with if it held the promise of returning a person to freedom,” Mickey Bergman, vice president of the Richardson Center, said in a statement.

“The world has lost a champion for those held unjustly abroad and I have lost a mentor and a dear friend.”

Richardson began his political career in earnest as an aide to then-Massachusetts Rep. Frank Bradford Morse before becoming a staff member for the US State Department and Senate Foreign Relations Committee in the 1970s.

He was first elected to the US House in 1983, representing New Mexico’s Third District. Richardson later served as US ambassador to the United Nations and secretary of energy before being elected governor of New Mexico in 2002. He served two terms before leaving office in 2011.

After an unsuccessful bid for the presidency in 2008, Richardson launched the Richardson Center for Global Engagement, a non-profit promoting international peace, in 2011.

Richardson and his namesake center had privately worked on behalf of families of hostages and detainees abroad. He traveled to Moscow last year and held meetings with Russian leadership to discuss the release of basketball star Brittney Griner and former US Marine Paul Whelan.

“On behalf of the countless families that Governor Richardson and his Center have helped, I wanted to express our profound feeling of loss at his passing,” Neda Sharghi, chair of the Bring Our Families Home Campaign, said in a statement Saturday.

“Governor Richardson has been a fierce advocate for human rights and the effort to bring home people unjustly held overseas.”

Democratic New Mexico Sen. Martin Heinrich said “Richardson’s legacy will have a lasting impact” in a statement on X, formerly known as Twitter.

“Gov. Richardson believed New Mexico could do big things. His ambition for our state meant he never accepted mediocrity and always pushed us to fight for the future we deserved. I was privileged to serve in his administration and will forever be grateful for all that he taught me,” Heinrich posted.

Richardson was born in 1947 in Pasadena, California. He grew up in Mexico City, Mexico, leaving to attend boarding school in Massachusetts in 1960.

He earned a bachelor’s degree in political science and French from Tufts University in 1970 and a master’s degree from Tufts’ Fletcher School of Law and Diplomacy in 1971.

He married Barbara Richardson in 1972 and had one daughter. — CNN