Colorado Gov. Jared Polis has ordered flags to fly at half-staff on Monday to honor the late U.S. Sen. Lindsey Graham.

Polis, a Democrat, cited the proclamation from U.S. President Donald Trump, who also ordered the American flag to be flown at half-staff at all federal buildings and grounds until July 18.

Graham died Saturday after a “brief and sudden illness,” his office said. He was 71.

Graham was one of the most influential figures in Washington on foreign policy, and he advised Trump on matters such as Iran and Russia. The senator had just returned from Ukraine and announced an agreement on Friday with the Trump administration to move forward on a package of Russia sanctions. He had been scheduled to appear on NBC’s “Meet the Press” on Sunday morning.

As chairman of the Senate Budget Committee, Graham played a central role during Trump’s second term as Republicans pushed major legislation on party-line votes while holding a narrow 53-47 majority in the chamber.

Under South Carolina law, Republican Gov. Henry McMaster will appoint a temporary replacement for Graham, who was seeking a fifth term in November.

Graham, who was elected to the Senate in 2002 after serving in the House, long promoted a policy of robust U.S. military interventionism and strong national defense that in later years would put him at odds with the growing isolationist wing of the Republican Party.

More recently, Graham had become well-known for his close ties with Trump, whom the senator briefly ran against for the party’s presidential nomination in 2016.

The Associated Press contributed to this article.