U.S. Senator Lindsey Graham, one of the Republican Party’s most influential voices on national security and foreign policy, has died at the age of 71 following what his office described as a brief and sudden illness.

Graham represented South Carolina in the U.S. Senate since 2003 after previously serving in the U.S. House of Representatives. During more than three decades in Congress, he became a leading figure on defense, judicial nominations and international affairs, earning a reputation as one of Washington’s most recognizable Republican lawmakers.

Over the course of his political career, Graham underwent a widely noted transformation from being a sharp critic of Donald Trump during the 2016 Republican presidential primary to becoming one of Trump’s closest allies in the Senate. He played a key role in advancing conservative judicial appointments, including the confirmation of Justice Brett Kavanaugh, and remained an influential voice on issues involving Ukraine, Israel, Iran and U.S. military policy.

A former U.S. Air Force officer and military lawyer, Graham also sought the Republican presidential nomination in 2016 before ending his campaign. At the time of his death, he was serving as chairman of the Senate Budget Committee and had recently secured the Republican nomination for another Senate term.

Tributes poured in from across the political spectrum and from international leaders. President Donald Trump remembered Graham as a “true American patriot,” while Ukrainian President Volodymyr Zelenskyy praised his steadfast support for Ukraine. Leaders from Israel, NATO and several allied nations also honored Graham’s commitment to U.S. national security and international alliances.

His passing leaves a significant vacancy in the U.S. Senate. Under South Carolina law, Governor Henry McMaster is expected to appoint an interim Republican successor until a special election is held.