US Senator Lindsey Graham, a key Republican who went from a vocal critic of ‌Donald Trump to one of his most loyal allies on Capitol Hill after Trump became US President, has died at age 71.

The South Carolina lawmaker died ‌after a “brief and sudden illness,” his office posted on social media platform X.

US media said emergency personnel had responded to a call for cardiac arrest ‌at Graham’s Capitol Hill home on Saturday night, local time.

Graham, just back from a trip to Ukraine, had been scheduled to appear on NBC’s Meet the Press program on Sunday, the network said.

Shortly after Graham’s death was announced, Trump called him “one of the greatest people and senators I have known” and a hard-working patriot.

Ukrainian President Volodymyr Zelensky said he was deeply saddened, calling Graham “a true defender of freedom and the values that make our world safer”.

During the 2016 US presidential election campaign, during which Graham was among many Republicans who lost the ‌nomination to 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 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.”

Later, after becoming a loyal supporter and frequent golf partner, Graham still publicly disagreed with Trump’s early 2025 decision to pardon about 1500 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 opponent of Iran.

“Israel has lost one of its greatest friends. America has lost a great patriot. I have lost a beloved friend,” Israeli Prime Minister Benjamin Netanyahu said.

Graham, a frequent visitor to Ukraine, met Zelensky in Kyiv on Friday. They discussed Ukraine’s air defence needs and a Russian ​sanctions bill, Zelensky said.

Zelensky noted that Graham had visited Ukraine 10 times since Russia’s full-scale invasion in 2022.

“We will always be especially grateful for the recognition of our people and words of admiration for the courage of Ukraine’s defenders,”  he wrote on social media.

Graham, a former US 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.