He made clear when he was appointed to fill McCain’s seat a few months ago that he wouldn’t run in the special election in 2020 to finish the final two years of McCain’s term. But there remained a mystery: Would he serve until then, or just a few months in a “placekeeper” role while Arizona Gov. Doug Ducey weighed a longer-term appointee?

Mystery solved.

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…

“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.”

There’s an obvious candidate to replace him. She’s known statewide from her recent run for Senate, winning more than a million votes on Election Day and losing only narrowly. She has legislative experience, having served in the House for the past four years. She’s a veteran, one who rose to the rank of colonel in the Air Force. And she has the enthusiastic support of Cocaine Mitch McConnell. It’s Martha McSally time.

Wait, what’s that? It’s … not Martha McSally time?

Arizona Gov. Doug Ducey has lost enthusiasm for appointing Rep. Martha McSally, a fellow Republican, to the Senate in recent weeks even as Republican leaders in Washington have championed her…

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.

I, for one, am shocked that a young politician who just lost a big election would issue a self-serving list of reasons for her defeat. What did Ducey want her to say in the memo, “I sucked”? That would have been dumb under any circumstance but especially dumb in the context of her being a top contender for the McCain vacancy. Admitting that she ran a bad race against Sinema would have handed the media a club with which to beat Ducey if he went ahead and appointed her to replace Kyl. Headline: “DUCEY APPOINTS ADMITTEDLY BAD CANDIDATE.”

Read down further into the WaPo piece that I excerpted and you’ll detect a whiff of some gubernatorial vanity at play. Apparently Team McSally’s memo tried to explain why Ducey himself easily won reelection as governor on the same day that she fell just short against Sinema. Instead of kissing ass by praising what a strong candidate he was, they chalked it up to him being an incumbent who was facing a weak progressive candidate. (Sinema by contrast strained to present herself as a centrist despite her very left-wing past.) McSally’s also apparently being knocked for having repositioned herself as a staunch Trumpist after being more standoffish towards him before her Senate run. But that was a matter of pure strategy: Running against two populists in the primary, she had no choice but to try to make herself acceptable to Trump fans by embracing their guy. It would have been political malpractice if she hadn’t and the GOP likely would have ended up with Kelli Ward as nominee.

The problem for Ducey is that there are no strong alternatives to McSally. The strongest candidate would probably be Ducey himself, but he just won reelection as governor and did so with the entire electorate believing that someone else would ultimately be appointed to replace McCain. Having him suddenly vacate the governor’s chair to join the Senate would look like an electoral bait-and-switch. His chief of staff, Kirk Adams, has been mentioned but Adams has only served five years in elected office as a state representative. He’s never run a statewide campaign and would have to run not one but two in order to secure a full term in the U.S. Senate: First he’d have to win the special election in 2020 to finish McCain’s term, then he’d have to win a full term in 2022. (If McSally ends up as the appointee after all, it’ll mean she’ll end up running three times for the same seat in the span of four years.) He could always choose someone from the McCain family but that’s probably Trump’s least favorite option among the ones available.

I think it’ll be McSally despite Ducey’s misgivings. McConnell usually gets what he wants and he wants her in the Senate, as she’s a known quantity politically and not the sort of populist who’ll end up being a pain in his ass. He’ll twist the arms that need twisting.