Bob Dole, a former U.S. senator and Republican presidential candidate, died Sunday morning, the Elizabeth Dole Foundation said. He was 98.

Dole was diagnosed with stage four lung cancer earlier this year and said he was starting treatment.

“It is with heavy hearts we announce that Senator Robert Joseph Dole died early this morning in his sleep,” the foundation said on Twitter.

Dole served as a U.S. senator for Kansas for nearly 30 years, starting an impressive political run. In 1976, he was Gerald Ford’s vice presidential nominee, though the pair was defeated by President Jimmy Carter and his running mate, Walter Mondale.

He began to test the waters for his own presidential run in 1980. He later clinched the GOP nomination for the presidency in 1996, losing to the incumbent, President Bill Clinton.

Prior to his political career, Dole served in the Army during World War II, during which he was seriously injured. He became temporarily paralyzed from the neck down, and spent years rehabbing at a military hospital. Dole regained much of his movement, but his arms never fully recovered.

Tributes poured in after the foundation announced Dole’s death.

“Bob was an American statesman like few in our history,” President Joe Biden said in a statement. “A war hero and among the greatest of the Greatest Generation. And to me, he was also a friend whom I could look to for trusted guidance, or a humorous line at just the right moment to settle frayed nerves. I will miss my friend. But I am grateful for the times we shared, and for the friendship Jill and I and our family have built with Liddy and the entire Dole family.”

Flags at the Capitol will fly at half-staff in honor of Dole, Speaker Nancy Pelosi’s office said Sunday.

“Senator Dole was a war hero, a political leader, and a statesman – with a career and demeanor harkening back to a day when members of the Greatest Generation abided by a certain code, putting country over party. His sharp wit was matched only by his integrity, and he lived his life in a way that made it clear just how proud he was to be an American, and how committed he was to making this country everything he knew it could be,” former President Barack Obama said in a statement.

President George W. Bush, whose father was considered a rival to Dole before George H.W. Bush’s funeral, said Dole “represented the finest of American values.”

“He defended them in uniform during World War II. He advanced them in the United States Senate. And he lived them out as a father, husband, and friend. Our entire family benefitted from that friendship, including my father. I will always remember Bob’s salute to my late dad at the Capitol, and now we Bushes salute Bob and give thanks for his life of principled service,” Bush said in a statement.

Former President Donald Trump hailed Dole as an “American war hero and true patriot.”

“He served the Great State of Kansas with honor and the Republican Party was made stronger by his service. Our Nation mourns his passing, and our prayers are with Elizabeth and his wonderful family,” Trump said in a statement.

Dole was one of the few elder Republican statesmen to have backed Trump in 2016. He stuck with the 45th president through the 2020 election. However, Dole told USA Today earlier this year, after he had been diagnosed with cancer, that he regretted that Trump and his allies pushed false claims about the election being stolen.

“I’m a Trumper,” he told the newspaper. Then, later in the same interview, he added: “I’m sort of Trumped out, though.”