Arizona Sen. Jon Kyl is officially stepping down on December 31

Just over a month after Arizona voters settled a hotly contested race for one of its Senate seats, its other one is now up for grabs.

Arizona Republican Sen. Jon Kyl — a former lawmaker who had been appointed to take over the remainder of late Sen. John McCain’s term — has announced that he plans to step down from the role on December 31, the Arizona Republic reports. This isn’t exactly unexpected — he’s long said he would only serve until January, for reasons some speculate have to do with his financial disclosures and past as a lobbyist.

”It has been an honor and a privilege to again serve the people of Arizona,” Kyl wrote in a December resignation letter to Arizona Gov. Doug Ducey, obtained by the Republic. “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.”

The resignation means that Ducey will have to pick someone new to cover the two years that are left until the seat is on the ballot again in 2020. (At that time, voters will have a chance to pick a candidate to take over McCain’s term until 2022.)

Kyl had previously served as Arizona senator for 18 years and returned to the upper chamber following McCain’s death this past August out of what he described as a “sense of duty.”

Ducey is now required to appoint a Republican to fill this vacancy, since state law dictates that the replacement must be of the same party as McCain and Kyl. While Republican representative and Senate runner-up Martha McSally had seemed like a possible favorite for the job earlier this year, Sean Sullivan reported recently at the Washington Post that her star has fallen:

There are several reasons McSally’s chances have faded, according to the people who spoke on the condition of anonymity to freely discuss private conversations. One is a post-election memo her campaign strategists provided to The Washington Post last month, which attributed her defeat in November to external factors. Among them: strong Democratic fundraising, a geographic disadvantage and voter hostility toward President Trump.

The memo sparked outrage inside Ducey’s circle and among broader swaths of influential Republicans, who felt her team did not own up to its strategic mistakes and was trying to deflect blame for her loss to Democratic Rep. Kyrsten Sinema.

According to the Republic, others that Ducey could be considering include former state Rep. Kirk Adams, who has also served as the governor’s chief of staff, as well as state treasurer Eileen Klein.

Ducey’s office said he’s on track to pick a replacement in the “near future,” something he’ll likely do ahead of the new congressional term on January 3.