There was something off about President Donald Trump’s decision to fire Secretary of State Rex Tillerson on Tuesday.

Back in the fall, the line of succession was supposed to look like this:

The Trump White House already had a plan to replace Tillerson with CIA Director Mike Pompeo and to replace Pompeo with Sen. Tom Cotton (R-AR).

Cotton was Trump’s “favorite” to take over the intelligence agency, per the New York Times.

If asked to serve, Cotton “does his duty when the country calls,” a friend of his told Axios.

But on Tuesday, when the president finally decided to fire Tillerson, it didn’t go quite according to plan. Pompeo was indeed elevated to the State Department — but Cotton was left in the Senate. Instead, Gina Haspel was named as Trump’s new CIA director. She will be, notably, the first woman nominated to the post and is a seasoned spy who briefly oversaw a torture black site in Thailand during the George W. Bush years, per CBS News.

So what happened? It depends on whom you ask. But the inescapable lesson is this: Trump’s administration has become so radioactive that the president can’t bring in one of his party’s most promising stars, one of his closest allies in the Republican establishment, to take such a prominent post.

The White House is in the midst of a scary staffing crisis, shedding officials who have mustered at least some experience running the federal government and failing to attract top talent to replace them. Cotton, whatever the reason for his being skipped over for the CIA directorship, is just the latest example of how the poisonous environs created by Trump are undermining his ability to build his own administration.

Why Gina Haspel is CIA director instead of Tom Cotton

There are at least three different theories out there to explain why Trump decided to tap Haspel to lead the CIA instead of Cotton. They aren’t necessarily mutually exclusive either; it could have been a combination of the following:

The White House didn’t want to open up Cotton’s Arkansas Senate seat after the GOP’s shocking loss in the Alabama Senate race and other special elections.

Cotton started to find the job less attractive given the possibility that Trump, a historically unpopular president, could lose in 2020.

With Cotton looking ahead to his own presidential campaign someday, staying in the Senate is a better platform for building and keeping a national profile than leading a covert intelligence agency.

Arkansas Senator Tom Cotton was at one point favorite to take over CIA. White House became hesitant to put another safe Senate seat on the table, source close to Cotton tells me, and job became less attractive to him as the window he’d serve in it shrunk assuming Trump loss in 20 — Eliana Johnson (@elianayjohnson) March 13, 2018

The fact that Tom Cotton is staying in the Senate rather than moving to the CIA is probably better for his long-term presidential hopes. @AdamWollner laid out the case back in January. ($$) https://t.co/0b3xNola83 pic.twitter.com/6eBHQ3WLm7 — Ben Pershing (@benpershing) March 13, 2018

However you look at it, the first two theories tell the same story: The national political environment is so unfavorable to Republicans that the White House had real fears that they could lose a Senate seat in Arkansas (a state Trump won by 27 points in 2016). And Cotton, as fervent a Trump true believer as you will find in the United State Congress, is harboring real doubts that his president can win again in 2020.

Why it’s important that Cotton was passed over

The wildest part is neither of those lines of thinking is illogical.

In December, Republicans lost an open Senate seat — one that Trump had also opened up by picking Jeff Sessions to be his attorney general — in Alabama, where Trump beat Hillary Clinton by an even bigger margin than he did in Arkansas. Sure, that might have been in part because the GOP nominee was a credibly accused child predator, but the Republican establishment has proven pretty bad at getting its preferred nominee elected in primaries. It was apparently too big a risk.

On Cotton’s end, looking ahead to 2020 and his own presidential ambitions, he should absolutely be wary of attaching himself too tightly to Trump. This is a president who, at the end of his first year in the White House, had the lowest approval rating ever even as the economy continued to perform relatively well. That is quite a feat, given how tightly the economy and presidential approval ratings are usually linked.

It is certainly true that the Senate probably is a better launching pad for a presidential campaign whenever Cotton decides to run — George H.W. Bush is the only CIA director to reach the White House. But that was already true back in October and November when the Cotton-to-CIA hype was its hottest and his friends were telling Axios that he would serve if called.

Something changed. The simplest explanation is that Trump’s political standing, even within his own party, has eroded to such a degree that the Arkansas Senate seat could be in jeopardy and Cotton now doubts the president’s reelection viability.

In Langley, maybe this doesn’t matter much. Haspel is certainly qualified, from a résumé point of view, and seems to share Cotton’s comfort with torture.

But the strange case of Tom Cotton and the CIA is emblematic of Trump’s struggle to attract, as he loves to say, the best people. It is a fierce ouroboros: Trump’s incompetence feeds his struggle to recruit his preferred candidates. Given the trajectory of his presidency, it is probably only going to get worse.