US Senator Lindsey Graham, a Republican who went from a ​vocal critic of Donald Trump to one of his most loyal allies after Trump became president, has died, his office announced on Sunday. He was ‌71.

The South Carolina lawmaker died after a “brief and sudden illness,” his office posted on X. US media said emergency personnel had responded to a call for cardiac arrest at his Capitol Hill home in Washington on Saturday night.

“It appears to have been a heart attack,” South Carolina Republican Senator Tim Scott told CBS News’ “Face the Nation” program.

The contest to succeed Graham will not impact the broader fight for control of the Senate ​in November between Republicans and Democrats, as South Carolina is a reliably Republican state.

However, his death robs Trump of a dependable Senate vote as the president seeks to ​push his agenda in the closely divided Senate.

“He’s a tough one to lose,” Trump told NBC’s “Meet the Press” program. “He was great. He was ⁠unique in every way.”

Another senior Republican in the upper chamber — Senator Mitch McConnell of Kentucky — remains hospitalised for undisclosed health problems.

Trump, speaking on CNN’s “State of the Union” program, said Graham, who had ​just returned from a trip to Ukraine, called him on Saturday night. “Other than being tired, he was fine,” Trump said.

The president said he received news of Graham’s death early Sunday morning.

Under South ​Carolina law, the state’s Republican governor, Henry McMaster, can immediately appoint a temporary replacement to fill Graham’s seat.

South Carolina Republicans must then also hold an expedited primary election to pick a nominee for the November midterm election. That nominee does not have to be the same person McMaster picks as a temporary replacement.

Staunch advocate for Ukraine, Israel

Graham, a defence hawk, was a prominent supporter of Israel and Ukraine and an opponent of ​Iran.

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

On Friday, Graham met Zelensky in Kyiv, ​and the Ukrainian leader said the two discussed Ukraine’s air defence needs and a Russia sanctions bill.

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

In a Facebook post, Zelensky ‌wrote: “We will ⁠always be especially grateful for the recognition of our people and words of admiration for the courage of Ukraine’s defenders.”

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

Netanyahu expects to attend Graham’s funeral, a senior Israeli official said.

Once bitter Trump critic

During the 2016 presidential campaign, in 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.”

Later, after becoming a loyal ⁠supporter and frequent golf partner, Graham still publicly disagreed with Trump’s decision upon returning to office last year 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.

“They did not always agree, but … ​they figured out how to have a friendship,” Scott told “Meet the Press.”

Graham recently served as chairman of the Senate Budget Committee.

When he ​chaired the Senate’s Judiciary Committee, ⁠Graham helped drive Trump’s judicial overhaul, presiding over the confirmation of more than 200 federal judges, a conservative legacy likely to last generations.

In 2018, Graham passionately defended Brett Kvanaugh, who was nominated by Trump for a seat on the US Supreme Court, amid sexual assault allegations against the nominee. Kavanaugh was narrowly confirmed to the high court.

Trump, in his CNN interview on Sunday, called it the “finest moment” ⁠of Graham’s ​Senate career.

A former Air Force lawyer and member of the South Carolina Air National Guard, Graham was elected to ​the Senate in 2002. Before that, he was elected to the House of Representatives in 1994.

He never married and lived in Seneca, South Carolina.