Graham was once a vocal critic of Donald Trump but later became a loyal supporter.
He was also a prominent supporter of Israel and Ukraine and an opponent of Iran.US senator Lindsey Graham, a key Republican who went from a vocal critic of Donald Trump to one of his most loyal allies after Mr Trump became president, has died at age 71.
The South Carolina lawmaker passed away after a "brief and sudden illness," his office posted on X early on Sunday.
A preliminary medical examiner finding shared by his office later confirmed his death was caused by a rupture to his aorta.
The rupture was related to the hardening of Graham's arteries.
An official cause of death will be disclosed after toxicological and microscopic testing.
NBC News said emergency personnel had responded to a call about a cardiac arrest at his Capitol Hill home on Saturday night.
Graham, just back from a trip to Ukraine, had been scheduled to appear on the "Meet the Press" interview program on Sunday morning, the network said.
Shortly after his death was announced, Mr Trump called Graham "one of the greatest people and senators I have known" and a hard-working patriot.
During the 2016 campaign, during which Graham was among many Republicans who lost the presidential nomination to Mr Trump, he posted on social media: "If we nominate Trump, we will get destroyed … and we will deserve it."
Graham told CNN in 2015 that Mr Trump was "a race-baiting, xenophobic, religious bigot," adding, "He doesn't represent my party. He doesn't represent the values that the men and women who wear the uniform are fighting for".
Lindsey Graham went from a vocal critic of Donald Trump to a staunch supporter. (AP: Alex Brandon)
Later, after becoming a staunch supporter, Graham still publicly disagreed with Mr Trump's early 2025 decision to pardon about 1,500 of the president's supporters who attacked the US Capitol on January 6, 2021, saying it could lead to more violence.
A defence hawk, Graham "consistently pushed for outcomes in the War on Terror that protect our long-term national security interests," his website said.
He was a prominent supporter of Israel and Ukraine and an opponent of Iran.
Israeli Defense Minister Israel Katz posted on X that he was deeply saddened by the death of Graham, "who stood with Israel at its most difficult moments".
Israeli Prime Minister Benjamin Netanyahu added his condolences, saying "Israel has lost one of its greatest friends. America has lost a great patriot. I have lost a beloved friend," in a statement.
An advocate for Ukraine
On Friday, Graham said China could play a decisive role in pressuring Russia towards peace talks, helping end its war in Ukraine.
Graham, a frequent visitor to Ukraine, met President Volodymyr Zelenskyy in Kyiv. They discussed Ukraine's air defence needs and a Russian sanctions bill, Mr Zelenskyy said.
Graham said bolstering Ukraine's military capabilities and aligning sanctions with a diplomatic push could force Moscow into talks.
"The road to ending this war, the road to peace, passes through Beijing more than it does [through] Washington, Kyiv, or Moscow," Graham told reporters at Kyiv's Mykhailivska Square.
"China has an oversized influence. I'd like them to use their influence for the good of the world.
"I don't believe [Russian President Vladimir] Putin is there yet, but it wouldn't take much to get him there."
Mr Zelenskyy wrote on social media he was "deeply saddened" by the news, calling Graham "a true defender of freedom and the values that make our world safer".
He noted that Graham had visited Ukraine 10 times since Russia's full-scale invasion in 2022.
Volodymyr Zelenskyy met Lindsey Graham in Kyiv on Friday. (Reuters: Ukrainian Presidential Press Service)
"We will always be especially grateful for the recognition of our people and words of admiration for the courage of Ukraine's defenders," Mr Zelenskyy said.
Graham recently served as chairman of the Senate Budget Committee and was a member of the Senate Committee on Appropriations, Senate Judiciary Committee and Senate Committee on Environment and Public Works.
Graham, a former Air Force lawyer and member of the South Carolina Air National Guard, was elected to the US Senate in 2002.
Before that, he was elected to the US House of Representatives in 1994 for South Carolina's 3rd congressional district, according to his website.
He was not married and lived in Seneca, South Carolina.
Reuters
