We may not be there yet, but there may come a point at which it’s very difficult to find well-qualified people willing to serve in President Trump’s Cabinet. And if we do, we’ll look back on Kirstjen Nielsen’s tenure as an early indicator.

The homeland security secretary appears set for an unceremonious exit less than one year after taking over the nation’s third-largest agency, report The Post’s Nick Miroff, Josh Dawsey and Philip Rucker. The writing has been on the wall for months — and her departure could possibly be delayed further — but Trump’s long-standing frustration with Nielsen and the freedom he now has with the 2018 elections behind him seem to be bringing this situation to a head. Trump has previewed a potential shake-up in recent weeks, and Nielsen was always among the most endangered top officials.

The looming decision is about Nielsen’s failure to meet Trump’s expectations when it comes to curtailing illegal immigration at the U.S.-Mexico border. An uptick in border apprehensions in recent months and the caravan of migrants coming up from Honduras have probably sealed Nielsen’s fate.

But she seems to be a victim of irrational expectations more than anything. And she has spent much of her tenure tolerating Trump’s whims and even putting her reputation on the line in the name to keeping her job. No amount of public fealty, it seems, has been enough.

Nielsen has repeatedly fed Trump’s narrative about the Russia investigation with misleading or incorrect comments. Like Trump, she declined to directly blame Vladimir Putin for Russia’s 2016 election interference, even though the U.S. intelligence community does. Months earlier, she was asked about that same conclusion and said: “I do not believe that I’ve seen that conclusion. . . . That the specific intent was to help President Trump win? I’m not aware of that.

She also suggested that Russia’s attacks an American election infrastructure weren’t necessarily aimed at helping Trump, even though the intel community says the broader effort was — a bizarre delineation clearly aimed at appeasing the boss, who has asserted that Russia actually favored Hillary Clinton.

During testimony in January, Nielsen declined to confirm Trump’s closed-door remarks describing African nations, Haiti and El Salvador as “shithole countries” — even though she was present. Then, in an exchange that followed, she was asked to account for Trump saying the United States needed more immigrants from Norway, an overwhelmingly white country. She even tried to pretend that she wasn’t sure Norway was an overwhelmingly white country and that Trump was referring to work ethic:

LEAHY: What does he mean when he says he wants more immigrants from Norway?
NIELSEN: I don’t believe he said that specifically. . . . What he was specifically referring to is, the prime minister telling him that the people of Norway work very hard. And so, what he was referencing is, from a merit-based perspective, we’d like to have those with skills who can assimilate and contribute to the United States, moving away from country quotas and to an individual merit-based system.
LEAHY: Norway is a predominantly white country, isn't it?
NIELSEN: I actually do not know that, sir, but I imagine that is the case.

By far the most controversial chapter of Nielsen’s tenure, though, has been the separation of migrant families at the border — a policy that led to the detention of children in large cages and the government’s failure to promptly reunite them with their families. Nielsen reportedly resisted the policy behind the scenes. But publicly, she boosted it and even made implausible arguments in favor of it. She even went so far as to argue that it wasn’t an actual policy.

“We do not have a policy of separating families at the border, period,” she said, laughably. A DHS inspector general’s report last month contradicted this and other claims Nielsen made about the policy’s implementation.

And that’s the thread that runs through all of this. Trump puts people like Nielsen in the position of accounting for his whims and his counterfactual claims. His expectations for how much someone like Nielsen could accomplish when it comes to securing the border were almost definitely unreasonable. She tried to compensate for those shortcomings by saying things she couldn’t possibly have believed to boost Trump.

If and when she is finally ousted, it should serve as notice to anybody who would succeed her, or anyone else in the administration, that fealty is a necessary but not sufficient part of the job. And there’s no guarantee that sacrificing your own reputation for Trump will be rewarded.