President Donald Trump, despite his reality TV reputation, has only fired two people — and in both cases, it's caused more problems for him than it solved.

So while he seems to be running out of patience with Attorney General Jeff Sessions — and is even exploring the possibility of firing him, according to the Washington Post and the AP — the president’s strategy so far appears to be to vent at length, and in public, about how mad he is with Sessions, without actually forcing him out.

On Tuesday, for the second day in a row, the president started his day by attacking his attorney general on Twitter. Tuesday’s tweets decried Sessions’ “very weak position on Hillary Clinton crimes,” and asked why Sessions wasn’t investigating purported Ukrainian efforts to help Clinton in the 2016 presidential campaign alongside the investigation into ties between the Russian government and Trump allies. (On Monday, the accusation was slightly different: that the “beleaguered” Sessions wasn’t investigating Clinton’s own ties to Russia.)

Last week, Trump told the New York Times that he wouldn’t have appointed Sessions to begin with if he’d known Sessions would recuse himself from the federal Trump/Russia investigation: “If he was going to recuse himself, he should have told me before he took the job, and I would have picked somebody else.”

Trump has been frustrated with Sessions, who was once one of his closest advisers, for months, ever since Sessions’s Russia-investigation recusal. And he certainly appears to be considering firing the attorney general — on Monday, the Post reported that Trump asked one advisor how it would play in “conservative media” if he cut Sessions loose, and whether he could mitigate the damage by picking another conservative like Texas Senator Ted Cruz. (Longtime Trump ally Rudy Giuliani has also been floated as a replacement; Trump reportedly told Giuliani that he could have the AG job weeks after it was offered to Sessions, and before this whole rigamarole began.)

But the famously-mercurial president hasn’t yet pulled the trigger yet. Without the actual “you’re fired!,” all this venting looks more than anything like a sustained effort to make Sessions’s life so miserable that the attorney general will decide to pick up and leave the administration.

At some point, Sessions might decide enough is enough. But the weeks of increasingly public rebukes he’s suffered raise questions about why he hasn’t already left. After all, it’s hard to imagine why someone would continue to serve a president who so openly demeans him and his running of his department.

The answer is that Sessions isn’t in the Trump administration primarily to serve Donald Trump. He’s there to enact a robust — even aggressive — policy agenda, aimed at protecting police officers, cracking down on unauthorized immigrants, and using criminal justice policy to send a “tough on crime” message.

It’s an agenda that falls in line with the law-and-order populism Trump espoused before arriving in office (and, less frequently, during his presidency). But before it was “Trumpism,” it was Sessions-ism. And Sessions’s commitment to the policies that first attracted him to Donald Trump’s presidential campaign certainly appears to outstrip his commitment to President Donald Trump.

Sessions is the rare Trump appointee more committed to Trumpism than he is to Trump personally

Most of President Trump’s Cabinet officials and top White House advisers fall into one of two camps. Either they’re fairly conventional establishment Republicans who didn’t have much connection to Trump before he was elected president (Health and Human Services Secretary Tom Price, Ambassador to the United Nations Nikki Haley) or they’re people who didn’t have much in the way of political experience before being appointed to serve in the Trump administration.

Some of these appointees were in business (Secretary of State Rex Tillerson). Some were in the military (Secretary of Defense James Mattis, Homeland Security Secretary John Kelly), where they had some experience with policy but much less with the political maneuvering that policy requires at the highest levels of government. Some were simply longtime Trump loyalists with little in the way of a discernible ideology, like first-son-in-law and trusted adviser Jared Kushner and Treasury Secretary Steve Mnuchin.

There are three big exceptions to this: people who were in Trump’s inner circle during the campaign, but who had careers in politics and policy before Trump came along. Not coincidentally, they’re also the most committed to the ideology known as Trumpism, a populist nationalism very hawkish on immigration and supportive of law enforcement as the protectors of law and order.

Two of those — Steve Bannon and Sessions protégé Stephen Miller — are in the White House. The third is Sessions, at the helm of the Department of Justice.

Sessions has decades of experience in the federal government, as a US attorney and a senator. But he’d never been in the Republican mainstream. While many in his party supported expanding legal immigration, Sessions stood firmly against immigration both legal and unauthorized; while other Republicans embraced criminal justice reforms like reducing mandatory prison sentences, Sessions remained a down-the-line “tough on crime” Republican.

Then Trump came along, and took the lead in the Republican presidential primary for taking a hard, culture-war-inflected line on immigration and a populist tone — a chance to take Sessions-ism mainstream.

Sessions was the first member of the Senate to endorse Trump, and helped the candidate shape his campaign platform; by Election Day, he was arguably the president’s closest adviser. He was rewarded with the attorney generalship.

Almost immediately after Sessions was confirmed, though, he recused himself from the Russia investigation after reports surfaced that he’d met with Russian Ambassador Sergey Kislyak during the campaign, and hadn’t reported those meetings during the confirmation process. Not only did Sessions not consult the president about his decision, but Trump reportedly found out about the recusal just before Sessions announced it to the public. In Trump’s eyes, he’s made clear, that means that Sessions’s top priority wasn’t necessarily protecting the president.

The extent to which Sessions has honored that recusal, especially when it comes to his involvement in firing Comey, has been debated. But the fact remains that he decided early in his tenure to sacrifice some control over a part of his job that would have allowed him to protect the president, in order to put a controversy behind him. That’s the action of someone who understands the way the Washington news cycle operates, and is sensitive to losing influence with members of his party in Congress (and officials in his own department) because he’s embroiled in scandal. But more fundamentally, it’s the action of someone whose top priority is to enact a policy agenda, rather than simply protecting his commander in chief.

Sessions is responsible for nearly all of Trump’s policy accomplishments. If he leaves, Trumpism may stagnate.

The irony of Trump concentrating his ire on Sessions is that the attorney general has been the most effective member of the administration by far.

On criminal justice, Sessions has instructed US attorneys to take a much more aggressive line in charging drug, gun, and immigration offenses than they previously had — including undoing an Obama-era policy that allowed attorneys to avoid charging drug offenders with the harshest possible sentence, and instructing prosecutors to stick a federal immigration charge on any defendant who’d entered the US illegally. He’s expanded police powers to seize property from people who haven’t yet been convicted of a crime — including in states whose governments have banned the practice. He’s frozen Department of Justice efforts to oversee police departments accused of overly aggressive or discriminatory practices.

And despite the fact that federal immigration policy belongs at least as much within the Department of Homeland Security’s purview as it does the Department of Justice’s, Sessions has taken the lead there as well. In addition to his instructions to attorneys on federal charges, Sessions has led the effort to define — and defund — “sanctuary cities” that don’t do as much as the administration would like to help enforce federal immigration law. (Sessions has taken to delivering speeches in so-called “sanctuary cities” like Las Vegas and Philadelphia to blame local governments for enabling violent crime.)

To actually see through these policy changes, though, Sessions will need to stay on the job. His memos to US attorneys don’t mean much unless more than a handful of US attorneys are actually in place around the country. And his biggest opportunity to overhaul immigration policy — forcing President Trump to end the Deferred Action for Childhood Arrivals (DACA) program — is about to come to the fore, in the face of threats by Republican state officials to sue the administration to end the program in September.

It’s possible that if Sessions resigned (and the Senate managed to confirm a replacement, which, depending on who the replacement was, might not be a foregone conclusion), the next attorney general would agree with his predecessor’s agenda. But it’s extremely unlikely that he would have the expertise and relationships to carry it out effectively. And it’s even less likely that promoting the Sessions-esque policy agenda would take up more of the next AG’s energy than defending President Trump.

The Trump presidency was an opportunity for Sessions to do what he’s been calling on the federal government to do for years: step in aggressively to promote social order by taking an uncompromising approach to law enforcement at the federal and local levels. He doesn’t need the personal confidence of the president to carry out that agenda. And if he decided to pick up and leave, he’d have every reason to believe the agenda would collapse behind him.

There is no Trumpism without Jeff Sessions. Trump may not know that, but Sessions probably does.