Former Sen. Tom Coburn, a Republican maverick from Oklahoma known for spotlighting government waste and fighting the national debt, died Saturday at the age of 72.

The physician-turned-politician cut short his Senate career after a recurrence of prostate cancer. He retired after the 2014 elections with two years remaining in his second term.

Coburn would continue his crusade against what he viewed as wasteful spending after leaving the Senate, and he also took up the cause of pushing for a Convention of States to consider amendments to the Constitution.

“He was respected by everyone for a lot of things—as a medical doctor, an intellectual, a fearless advocate against government waste, a sought after advisor—but more than that, he was a brother in Christ,” Oklahoma GOP Sen. James M. Inhofe said in a statement Saturday. “I was honored to serve the people of Oklahoma with him, and Kay and I are praying for Carolyn and the rest of his family in their time of grief.”

“Tom felt a strong call to serve his fellow Oklahomans as both a physician and an elected official. He did both with genuine personal integrity. In Oklahoma and far beyond, Tom became a legendary figure who fiercely fought for what he believed in and what he thought was best for future generations of Americans. And he did so with great conviction and resolve,” Rep. Tom Cole, R-Okla., said in a statement after learning of Coburn’s death.

Following his 2004 election to the Senate, Coburn bonded with a freshman Democrat named Barack Obama. Years later, when his friend was president, Coburn suggested Obama was “getting perilously close” to actions fitting the constitutional standard for impeachment.

Despite their deep partisan differences, though, Coburn told CBS’ “60 Minutes” that Obama was “a genuinely very smart, nice guy” and “a neat man.”

“You don’t have to be the same to be friends,” Coburn said in a “60 Minutes” interview. “Matter of fact, the interesting friendships are the ones that are divergent.”

At the time of Coburn’s retirement, Obama said of his former colleague “Even though we haven’t always agreed politically, we’ve found ways to work together — to make government more transparent, cut down on earmarks, and fight to reduce wasteful spending and make our tax system fairer. The people of Oklahoma have been well-served by this ‘country doctor from Muskogee’ over the past nine years.”

Perhaps known best for his “Wastebook” reports of federal programs that he considered to be squandering taxpayer dollars, Coburn earned the nickname “Dr. No” for picking at programs if there was no way to pay for them. His reports chronicled government funding for such items as studies of rabbits who receive Swedish foot massages and how long shrimp could run underwater on a treadmill, as well as a State Department program aimed at humiliating terrorists with tweets.

Coburn’s own Republican colleagues were not spared his wrath.

He eschewed GOP establishment picks George W. Bush and John McCain to endorse commentator Alan Keyes for president in the 2008 campaign. In his book, “Breach of Trust: How Washington Turns Outsiders Into Insiders,” Coburn and his longtime spokesman John Hart were unsparing in their criticism of business as usual.

In a statement released Saturday, Hart said of his former boss “He lived every day as if it were his last and took grand stands without grandstanding. It was never about him. He took on all sides and was loved by all sides. A model and mentor for the ages.”

Coburn first came to Washington as part of the historic Republican Revolution that took control of the House in 1995. He took part in the unsuccessful coup aimed at toppling then-Speaker Newt Gingrich, who had led the GOP to power after 40 years in the minority.

Even as he bade a tearful farewell to the Senate at the end of 2014, Coburn blocked action on popular, bipartisan legislation aimed at preventing suicide among military veterans because he said its $22 million price tag came with no offsets and duplicated existing Veterans Affairs programs. The measure did not head to Obama’s desk until February 2015, about a month after Coburn was out of office.

“To those of you over the years that I have offended, I truly apologize,” Coburn said in his Senate farewell address. “And I think none of that was intended because I actually see things different. I believe our founders were absolutely brilliant and far smarter than us. I believe the enumerated powers meant something.”

Coburn had spent a decade in his family’s optical business before going to medical school in his mid-30s. As a physician, he delivered 4,000 babies and challenged the congressional ban on outside income for professional services.

He found ways as both a House member and senator to keep seeing patients, and at one point finally doing so for free to not break the congressional rules.

He won his first House race in 1994 – succeeding Democrat Mike Synar, also known as a party maverick – and kept his promise to serve only three terms. Coburn returned to politics in 2004 to seek the Senate seat of the retiring Don Nickles, the GOP’s No. 2 leader as minority whip.

A devout Christian, Coburn took heat for helping to cover up his roommate Sen. John Ensign’s extramarital affair with the wife of a staffer.

Ensign, a Nevada Republican once touted as a potential presidential candidate, resigned in 2011 – the day before he was to testify before the Senate Ethics Committee about his affair with Cynthia Hampton. Coburn was admonished by the ethics panel for a meeting he had with Doug Hampton, Ensign’s former aide.

Couburn’s family announced his death in a statement, saying “Because of his strong faith, he rested in the hope found in John chapter 11 verse 25 where Jesus said, ‘I am the resurrection and the life. The one who believes in me, will live, even though they die.’ Today he lives in heaven.”

Niels Lesniewski contributed to this report.