Jon Kyl, former Republican U.S. Senator, will return to Capitol Hill as late Sen. John McCain’s successor.

Kyl retired in 2013 after rising to become the second-highest-ranking Republican senator. He served alongside McCain during his 18 years in the U.S. Senate. A representative for Ducey has confirmed that Kyl has agreed to serve through the end of the year. If Kyl opts to step down at the end of session, Ducey would appoint another replacement.

Ducey’s goal for an appointment was someone who could step into the seat to wrap up McCain’s unfinished business. Kyl brings a rich history and knowledge on key Arizona issues and is well respected among Republicans

“There is no one in Arizona more prepared to represent our state in the U.S. Senate than Jon Kyl,” Ducey said in a statement. “He understands how the Senate functions and will make an immediate and positive impact benefiting all Arizonans. I am deeply grateful to Senator Kyl for agreeing to succeed his friend and college of so many years.

“Every single day that Jon Kyl represents Arizona in the United States Senate is a day when our state is being well-served.”

Kyl represented Arizona in the U.S. Senate from 1995 through 2013, where he served as minority whip. Before becoming a Senator, he served in the House of Representatives from 1987 to 1995. In 2006, Time magazine named Kyl one of America’s 10 best senators.

After leaving the Senate, Kyl joined the Washington, D.C., law firm Covington & Burling. As senior adviser, he helps clients with issues ranging from tax, national security, health care, defense, and intellectual property.

“Kyl felt a sense of service, largely because it was John McCain’s seat and he had served with him for so long,” the aide said.

Kyl is expected to be sworn in as early as Tuesday night or Wednesday.