Michael Busch, a champion of the Chesapeake Bay and progressive causes during his record-tenure as Maryland's Democratic House speaker, battled for the environment up until the end of his life. He died Sunday at age 72.

His environmental policies were especially high-profile in his final days as he sponsored a bill to permanently protect five oyster sanctuaries under Maryland law. The measure drew a veto from Gov. Larry Hogan, but the House overrode the veto Friday, and the Senate was expected to vote on an override Monday — the last day of the legislative session.

Bush died after developing pneumonia arising from a follow-up procedure to a 2017 liver transplant after being diagnosed with nonalcoholic steatohepatitis, a liver disease. He also had heart bypass surgery in September, after experiencing shortness of breath. Chief of staff Alexandra Hughes said Busch died surrounded by loved ones.

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Alison Prost, the Maryland executive director of the Chesapeake Bay Foundation, praised Busch's legacy of defending the waterway's fragile ecosystem.

"The Chesapeake Bay lost a champion today," Prost said. "While there were many issues that were near and dear to Speaker Busch, he elevated saving the Bay to a priority for the General Assembly, and legislators followed his lead."

"The Chesapeake Bay lost a champion today. While there were many issues that were near and dear to Speaker Busch, he elevated saving the Bay to a priority for the General Assembly, and legislators followed his lead." — Alison Prost, Maryland executive director, Chesapeake Bay Foundation

Busch also fought for expanded health care, educational improvements and other issues as Maryland's longest-serving House speaker. He was elected to the speakership in 2003.

"Nobody has done more to expand health care access and improve public health in Maryland than Speaker Mike Busch," said Vincent DeMarco, president of Maryland Citizens' Health Initiative.

A progressive Democrat, Busch as speaker oversaw Maryland's approval of same-sex marriage and the repeal of the death penalty. Legislation raising the state's minimum wage was passed twice under his House leadership.

Maryland Senate President Thomas V. Mike Miller called Busch a model delegate who cared for every corner of the state.

"My heart is broken for Mike Busch's family, the State of Maryland, and the Speaker's extended family — elected officials and staff that he has been a mentor and coach to over his time in public service," said Miller, a Democrat who has been battling prostate cancer. "Mike has been a friend for years, and has led the state to new heights of environmentalism and education."

Hogan, a Republican, ordered flags flown at half-staff for Busch, calling him "a giant in our government."

"Speaker Busch and I came from different sides of the aisle, but we often came together in the best interests of the people of Maryland," Hogan said. "He served with the decency and good nature of a teacher, a coach, and a family man. I was honored to ... work closely with him."

It's unclear when the House will choose Busch's successor. The speaker is elected by the 141 House members. Since Busch's absence last month, Del. Adrienne Jones has presided as speaker pro tem.

Busch was first elected to the House in 1986. His district included the state capital of Annapolis, making him a frequent presence in the State House — even when the General Assembly wasn't in session.

He was known as a consensus builder and good listener, qualities that helped him manage the diverse chamber.

Busch had a strong commitment to equal rights that resulted from growing up in the 1960s during the height of the civil rights movement against racial segregation.

"That was ingrained in me from my grandparents to my parents and through the '60s," he told The Associated Press in 2002.

At the time, he recalled two pictures on his grandparents' mantel — Jesus and Franklin D. Roosevelt. Both sets of grandparents "believed that Roosevelt gave average people a piece of the American dream," he said. "I really believe government is there to give people opportunity."

Busch, a Catholic, was born in Baltimore, and lived in Anne Arundel County from age 10 until he left for college.

He was a record-setting running back at Temple University in 1969, peaking in his junior year when he ran for 185 yards in a game. But for a leg injury, he might have pursued a pro career. The Dallas Cowboys sent him a letter telling him "you are being considered by our ball club as one of our top draft choices," but the team didn't know his career was already over.

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After getting a degree in education, he returned home and taught in public and parochial schools. He was a football and basketball coach at St. Mary's High School in Annapolis before quitting teaching in 1979.

His interest in politics was whetted in 1982 when he was a driver for Robert Pascal, an unsuccessful Republican candidate for governor. Busch finished fifth among 12 Democrats running for three House seats that year, then won in 1986.

Funeral arrangements weren't immediately disclosed.