Sen. Jon Kyl (R-Ariz.) will resign from the Senate on Dec. 31, leaving Arizona Gov. Doug Ducey (R) to fill the late Sen. John McCain John Sidney McCainThe Memo: Trump's strengths complicate election picture Mark Kelly: Arizona Senate race winner should be sworn in 'promptly' Cindy McCain: Trump allegedly calling war dead 'losers' was 'pretty much' last straw before Biden endorsement MORE's (R) seat for a second time.

Ducey’s office announced Friday that Kyl’s resignation letter was hand-delivered to his office on Thursday afternoon. His office said that he’ll make an announcement about appointing Kyl’s replacement “in the near future.”

Kyl, who initially served in the Senate from 1995 to 2013, was appointed in September to fill McCain’s seat after he passed away from brain cancer in August. Before his return to the Senate, Kyl worked as lobbyist for the Washington-based firm Covington & Burling.

ADVERTISEMENT

“Senator Kyl didn’t need to return to the Senate. His legacy as one of Arizona’s most influential and important political figures was already without question,” Ducey said in a Friday statement.

“But he did return, and I remain deeply grateful for his willingness to step up and serve again when Arizona needed him. I wish him and his family all the best.”

When joining the Senate this fall, Kyl had hinted that he planned to only serve in the Senate until year’s end.

Prior to Kyl’s announced departure on Friday, speculation was already swirling about whom Ducey would tap to replace him.

Ducey has remained mum on that decision, but outgoing Rep. Martha McSally Martha Elizabeth McSallyThe Hill's Campaign Report: Presidential polls tighten weeks out from Election Day Mark Kelly: Arizona Senate race winner should be sworn in 'promptly' New ABC/WaPost poll finds Trump edging Biden in Arizona, Florida MORE (R-Ariz.), who narrowly lost a heated Senate race in November, is considered a top prospect.

Another potential name is Kirk Adams, Ducey’s chief of staff who recently departed the governor’s office.

There will be a special election in November 2020 to serve out the remaining two years of McCain’s term.