Jon Kyl will resign from the Senate on Dec. 31, setting up another appointment to John McCain's seat

U.S. Sen. Jon Kyl will resign from the U.S. Senate on Dec. 31, The Arizona Republic has confirmed, setting up a second appointment by Gov. Doug Ducey to the seat once occupied by the late John McCain. 

Ducey is required under law to name another Republican to the seat. A replacement to the Senate seat "will be announced in the near future," according to the Governor's Office. 

Kyl wrote a letter dated Dec. 12 to Ducey, informing him of his resignation. The letter was hand-delivered to the Governor's Office late Thursday afternoon. 

"Thank you for appointing me to the U.S. Senate to fill the vacancy created by John McCain's death," Kyl wrote. "It has been an honor and a privilege to again serve the people of Arizona. 

"When I accepted your appointment, I agreed to complete the work of the 115th Congress and then reevaluate continuing to serve. I have concluded that it would be best if I resign so that your new appointee can begin the new term with all other Senators in January 2019 and can serve a full two (potentially four) years. Therefore, I will resign from the U.S. Senate effective 11:59 p.m. EST December 31, 2018."

Kyl succeeded McCain to the seat in September, after McCain's Aug. 25 death, with the understanding that he would serve at least until the end of the year and possibly until 2020, when the seat was on the ballot again. It became clear in recent weeks, as Kyl was hesitant to discuss his future in the Senate, that he would be leaving. 

Kyl, who served alongside McCain during his 18 years in the U.S. Senate, retired from the chamber in 2013 after rising to become the second-highest-ranking Republican senator.

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In a statement, Ducey praised Kyl's second stint on Capitol Hill, saying he served with "integrity and statesmanship" as the nation faced important issues. 

“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."

It is unclear if Kyl intends to return to joined the high-powered Washington, D.C., law firm Covington & Burling. As senior adviser, he helped clients on issues including taxes, health care, defense, national security and intellectual property.

The governor and his aides have been tight-lipped about who may be under consideration to replace Kyl.  

There is intense interest from Senate Majority Leader Mitch McConnell, R-Kentucky, for Ducey to appoint outgoing Rep. Martha McSally, the Republican who lost to Democratic Rep. Kyrsten Sinema for Arizona's other U.S. Senate seat. Sinema will be sworn into office Jan. 3.

Republican donors spent millions of dollars McSally's election effort and likely want to see that investment pay dividends. Ducey and McSally met recently, but it is unclear if there was discussion about a Senate appointment.

Other names have been mentioned as well, including Ducey's former chief-of-staff, Kirk Adams, and state Treasurer Eileen Klein. 

Ducey will have to weigh pressure from power players in the White House and on Capitol Hill against advice by friends, staffers and other voices in Arizona.

It is not known if Ducey has discussed his next appointment to the seat with McCain's widow, Cindy McCain.

Martha McSally met with Cindy McCain Friday afternoon at her north Phoenix home, according to Republicans familiar with the conversation.

In the meeting, McSally apologized for not mentioning the senator’s name during President Donald Trump's signing of the John S. McCain National Defense Authorization Act for Fiscal 2019. McSally did not use McCain's name in discussing the act when it was signed in August.

Cindy McCain expressed her appreciation for the apology and conveyed the importance of her late husband’s legacy and his service to Arizona, they said.

The two women did not speak directly about the Senate appointment, the Republicans said.

The meeting lasted about 30 minutes.

Follow the reporter on Twitter and Facebook. Contact her at yvonne.wingett@arizonarepublic.com.