Former Vermont U.S. Sen. James Jeffords, a long-running Republican congressman who later turned Independent, died on Monday at the age of 80.

Diane Derby, a former aide to Jeffords, announced that his health was deteriorating and that he died in Washington.

After working on Capitol Hill for more than 30 years, Jeffords retired from the U.S. Senate in 2006 while in the early stages of Alzheimer's disease, reports USA Today. He then lived out the rest of his days at a retirement home in the Washington, D.C. area.

"The passing of Senator Jim Jeffords will be felt throughout Vermont and our country," said Gov. Peter Shumlin in a statement. "We need more like Senator Jeffords. My heart goes out to his children and extended family."

Jeffords' children, Laura Jeffords and Leonard Jeffords, also released a statement Monday afternoon saying:

"While we are saddened by our father's passing, we take comfort in the knowledge that he lived a full life, from the hills of Vermont to the halls of Congress. We will miss his kindness, his good humor, and his generosity of spirit," reports the Associated Press.

After graduating from Yale and Harvard Law School, Jeffords was elected to a statewide office position as attorney general in 1968.

In 1974, he was elected to the House of Representatives as a Republican but he quickly stood out for his moderate and liberal-leaning views on education, the environment and help for people with disabilities. He was the only House Republican to vote against President Ronald Reagan's historic 1981 tax cuts. He was also a vocal critic of his party's shift to the Right and a number of President George W. Bush's policies.

After President George W. Bush rejected the Individuals With Disabilities Education Act, he decided to leave the Republican Party for good and caucus with the Democrats in May 2001.

At the time, he complained that GOP leaders "were set out on an agenda that did not fit into what the average American wanted to see."

"For more than 30 years, Jim has fought to do the right thing, standing against extremism," said former Vermont Gov. Howard Dean when Jeffords announced his retirement. "His work ethic, patriotism and commitment to serving the people of Vermont have made him a model to all of us who know him and have had the honor to work with him."