(CNN) -- Former U.S. Sen. Howard Baker, a one-time towering political figure in Washington who also served presidents and famously asked during the Watergate scandal what Richard Nixon knew and "when did he know it," has died.
He was 88.
A Tennessee Republican, Baker made his political mark over four decades, serving as majority leader and also ran for president in 1980.
Baker's former press secretary, Tom Griscom, confirmed that he died on Thursday.
A statement released by Baker's wife, former Sen. Nancy Kassebaum, and his two children from his first marriage, Darek Baker and Cynthia (Cissy) Baker, said his death was a "time of sorrow and also a time for the celebration of a remarkable life."
Senate Minority Leader Mitch McConnell said he would be remembered "with fondness by members of both political parties."
Baker was first elected to the Senate in 1966 and led the chamber from 1981-85. He was Reagan's chief of staff from 1987-88, and was ambassador to Japan under President George W. Bush.
President Barack Obama said in a statement that Baker's unofficial role as the "Great Conciliator" had "won him admirers across party lines, over multiple generations, and beyond the state he called home."
Former President George H.W. Bush said Baker was "adept at listening to the other guy state their position as he was at articulating his own."
CNN Chief Political Analyst Gloria Borger said Baker thrived an era when Democrats and Republicans often compromised to get things done in Washington.
"He was one of those senators who could walk across the aisle, cut deals and he was respected on both sides," Borger said. "Today in the Republican Party, that would be taken as a negative."
Former first lady Nancy Reagan said in a statement that she and her husband had "the greatest respect" for Baker's dedication to service.
"Howard was one of Ronnie's most valued advisers, his integrity and ability to create cooperation between the Congress and the White House was unparalleled," she said. "Most importantly, though, he was a good and trusted friend."
Baker also played a key role in the Watergate investigation that led to the downfall of President Richard Nixon.
As the vice chairman and ranking Republican of the investigation into Nixon's connection to the 1972 break-in at the Democratic National Committee headquarters in Washington, Baker famously asked "what did the President know and when did he know it."
CNN's Kevin Bohn contributed to this report.