Retirement also preserves the 83-year-old's legacy by allowing him to avoid a bruising re-election battle that would have broken his promise not to seek an eighth term.
Hatch first won election to the Senate in 1976, when he made a case to voters that three-term Democrat Frank Moss had been in office too long. Hatch went on to become one of the longest-serving senators in U.S. history, repeatedly telling voters that his experience made him all the more effective.
"Why would Utah give up its clout and power," Hatch asked during his 2000 re-election campaign, "just because someone says term limits are a good thing?"
Utah's other longtime senator, Republican Bob Bennett, who had worked across the aisle, was ousted during a 2010 backlash against the GOP establishment fueled by the tea party. Two years later, Hatch overcame a tough primary challenge and pledged that his next six years in office would be his last.
He flexed his political muscle during the last two years, serving as chairman of the powerful Senate Finance Committee and steering passage of the tax overhaul that was signed into law in December. He also led an effort to persuade Trump to take the rare step of scaling back the national monuments, which Utah's Republican leaders complained had locked up too much land.
"Look what just happened on the monuments," Former Utah Rep. Enid Greene Mickelsen said Wednesday. "You can love it or hate it, but it wouldn't have happened without Orrin Hatch. Simply would not have happened."
Trump used his announcement about the monuments to hail Hatch as "a true fighter" and to encourage him to run again.
Hatch's departure from the political stage opens the door for frequent Trump critic Mitt Romney, who has expressed interest in Hatch's seat.
Romney, the former Republican presidential candidate and Massachusetts governor, now lives in Utah, where he's fondly regarded as the man who helped turn around Salt Lake City's scandal-plagued 2002 Winter Olympics. He's also one of the most famous and respected Mormons in the world - a big deal in a state where 60 percent of residents belong to The Church of Jesus Christ of Latter-day Saints.
During the last presidential campaign, Romney called then-candidate Trump "a fraud" who had "neither the temperament nor the judgment to be president."
Hatch aligned himself with Trump despite the real-estate mogul's lukewarm reception among Utah Mormons and conservatives who place a premium on civility and were turned off by the president's brash demeanor, name-calling and his comments about women and minorities.
In 2016, Hatch endorsed Trump and later called him "an extraordinary man" and "one of the best I've served under." By ushering through tax reform, Hatch helped deliver the president's first major legislative achievement.
The tax legislation, along with his efforts to dismantle the monuments and his flirtation with another term drew a blistering editorial from The Salt Lake Tribune last week. Utah's largest newspaper said Hatch had an "utter lack of integrity that rises from his unquenchable thirst for power."
Hatch, known as a staunch conservative, had a close friendship with the late liberal lion Massachusetts Sen. Ted Kennedy. He worked with the Democrat to pass the American Disabilities Act and the Children's Health Insurance Program.
"If you look at the most significant human service-related legislation in the last 40-years, you'll see Orrin Hatch's name somehow associated with it, which I think will be a major part of his legacy," former Utah Gov. Mike Leavitt said Wednesday. "If a dictionary were to define compassionate conservative, they would cite Orrin Hatch as an example."
Hatch, a Mormon, frequently wrote religious songs and recorded music as a way to relax. One of his songs, "Unspoken," went platinum after appearing on "WOW Hits 2005," a compilation of Christian pop music.
He also ran for president in 2000 but backed out of the race for the Republican nomination after winning only 1 percent of the vote in the Iowa caucuses.
As the chairman of the Senate Judiciary Committee, he confirmed nearly 1,900 federal judges and was at the center of many of the biggest confirmation fights, including President Barack Obama's blocked Supreme Court nominee, Merrick Garland, and Clarence Thomas' Supreme Court confirmation hearings in 1991.
During the Thomas hearings, he was known as the senator who read aloud from "The Exorcist" to suggest that Anita Hill lifted details of her sexual harassment allegations from the book.
Hatch would have faced an ugly fight to win re-election, but it's "an extraordinary thing in American political life today" for someone to walk away at the height of his power, Mickelsen said.
"People will say he did it under pressure, but in the end, he chose to go out on his terms," she said.
Hatch announced his decision Tuesday by saying he's always been a fighter, "but every good fighter knows when to hang up the gloves."
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