President Donald Trump has strained his populist base this week with the threat of dismissing his Attorney General, former Sen. Jeff Sessions, implicit in a series of disparaging public statements.

Trump has repeatedly voiced his frustration with the head of his Department of Justice (DOJ) for inaction on alleged crimes by former Secretary of State Hillary Clinton. The Washington Post reports (via anonymous sources, so take it with a grain of salt) that Trump has even wondered to his aides how conservatives would react if he fired Sessions.

If Trump does fire Sessions, who could he nominate as a replacement?

If Trump wants someone to continue Sessions’ rock-solid work of enforcing his agenda–particularly on immigration–and also fight hard against career bureaucrat saboteurs (aka the “Deep State”), the answer is: virtually no one. If he wants someone who the Senate would actually confirm, he could pick any establishment-friendly organism, vertebrae or no.

With a seemingly hostile special counsel team, led by Robert Mueller, fishing for crimes to pin on Trump and his associates, the president’s new pick for DOJ would be politically radioactive no matter their qualifications. The political establishment would tarnish any moderately conservative nominee as Trump’s way of firing Mueller and — even if it is wholly warranted — quashing the left’s beloved investigation into Russia, “election hacking,” and whether Trump is a Manchurian candidate via golden shower blackmail tapes.

And, while Trump could attempt a recess appointment, Democrats are already promising to fight him tooth and nail on that front. And if Republicans cannot pass a healthcare bill, the president may not even have a recess to exploit.

Without a new nominee, who is the acting Attorney General?

That would be Rod Rosenstein, who Trump appointed as Deputy A.G. and previously served under presidents Bush (44) and Obama — the same Rod Rosenstein who recommended President Trump fire FBI Director James Comey, appointed a close personal friend to Comey as special counsel, and has not batted an eye at the special counsel’s Clintonista hires.

Talk radio mogul Rush Limbaugh has advised President Trump to focus his ire on Rosenstein instead of Sessions, arguing that the Deputy A.G.’s handling of the Russia probe suggests a “setup” to take down the president:

Because it’s Rosenstein that did not put any limits on Mueller as far as where he can look and what he can look for. Under normal circumstances, there would be a crime. Let me illustrate it this way. According to the Justice Department regulations… Let’s say there is a crime. Pick a crime, and it’s been established that a crime was committed. They appoint a special counsel. He’s investigating it. If, in the investigation, he comes across another crime, he cannot go look at it.

He cannot include it in the original charge. In that instance, he has to go back to the attorney general or deputy attorney general who appointed him. In this case it’d be Rosenstein. He has to go back and get permission to follow up this newly discovered crime. That’s how normally focused and limited these things are. This whole thing is — well, it doesn’t do it justice to call it a joke. It’s worse than that. This is obviously a setup.

Trump has also expressed distrust in Rosenstein, so he may take Limbaugh’s advice to heart.

If Trump fires Sessions and Rosenstein, who is the acting Attorney General?

The responsibility then falls to Rachel Brand, the current U.S. Associate A.G. She previously served in President Bush (44)’s DOJ and Privacy and President Obama’s Civil Liberties Oversight Board (PCLOB).

With her relatively low public profile, Brand’s ideology is a bit of a wild card. Democrats united in opposition to her nomination earlier this year, calling her “pro-corporate.” She helped Bush’s Supreme Court nominees, John Roberts and Samuel Alito, prepare for their confirmation hearings — which highlights the dilemma of entrusting the DOJ and thus the special counsel to her. Is she solidly conservative, like Alito, or is she malleable to swamp pressure, like Roberts?

Or, potentially even worse, is Brand solidly conservative but a “Never Trump”-er hostile to the presiden’t nationalist populism?

That is the gamble Trump will have to take if he removes Sessions and still hopes to move forward with his agenda.

Ian Mason contributed to this report.