Sen. Jon Kyl, R-Ariz., officially announced Friday that he will resign from the Senate at the end of the year, setting up another appointment for Arizona Gov. Doug Ducey to fill the late Sen. John McCain's seat.

Ducey announced that Kyl, 76, submitted his resignation in a hand-delivered letter Thursday, effective on Dec. 31, after temporarily taking the seat in September. Kyl had originally left the Senate in 2012 after three terms in the upper chamber.

“Senator Kyl didn’t need to return to the Senate," Ducey said in a statement. "His legacy as one of Arizona’s most influential and important political figures was already without question. 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 Jon Kyl returned to the Senate in September, our country faced many critical issues. Arizona needed someone who could hit the ground running from day one and represent our state with experience and confidence – and that’s exactly what Senator Kyl has done," Ducey continued. "Over the last few months, Senator Kyl served with the same integrity and statesmanship that marked his 26 years in Congress."

Kyl had long been expected to leave at the end of the year after only agreeing to fill McCain's seat through the end of the 115th Congress.

The looming vacancy sets up another appointment for the seat. Rep. Martha McSally, R-Ariz., who lost the November election to Sen.-elect Kyrsten Sinema to fill the seat vacated by Sen. Jeff Flake, R-Ariz., is viewed as a top choice to replace Kyl.

Kirk Adams, the former chief of staff to Ducey and a former speaker of the Arizona state house, is also a possible pick. Friday is also Adams' last day as Ducey's chief.

The governor's office added that a replacement will be named "in the near future."