The Trump-Sessions feud isn’t about personalities. It’s about whether the AG should protect him and go after his opponents.

The start of the most serious political crisis of Donald Trump’s presidency yet could be playing out right in front of our eyes.

President Donald Trump has been furious at Attorney General Jeff Sessions for months because Sessions recused himself from overseeing the Russia probe. And in recent days, that criticism has spilled into public view as the president has publicly mocked and criticized Sessions in an apparent effort to force him to quit.

The latest salvo from the president was a Wednesday morning set of tweets complaining that Sessions had not fired Deputy FBI Director Andrew McCabe, who is now serving as acting FBI director while Trump’s replacement for James Comey awaits confirmation:

Trump is inaccurately referring to money that Virginia Gov. Terry McAuliffe helped raise for the unsuccessful campaign of McCabe’s wife for a seat in the Virginia state senate (McAuliffe is a Clinton friend, but he doesn’t need that as a motivation to try to help a Democratic candidate win a state senate seat).

But the Trump/Sessions feud isn’t just a dust-up about personalities — it’s reportedly part of a larger effort by Trump’s team to exert more political control over the Justice Department, with an eye toward potentially shutting down special counsel Robert Mueller’s investigation into Trump associates’ Russia ties.

Even beyond the specific Russia investigation, Trump’s fury at Sessions seems born of a conviction that the United States Justice Department should be an extension of the president’s will, down to determining whom and what they investigate.

According to his own words, splayed out on Twitter for all to see, Trump really wants his Justice Department to more aggressively investigate his political opponents: Hillary Clinton and Democrats. He has made it very clear that this is what he wants, and he would presumably make it a top consideration in selecting a replacement for Sessions.

If Trump can actually manage to make this happen — by installing cronies at the Justice Department who will shut down investigations he doesn’t like and start up ones he wants — it would mean a remarkable slide into illiberalism, and it would violate decades’ worth of norms in American government and about the rule of law.

And potentially the scariest thing of all is that he might just be able to get away with it — unless Republicans in Congress stand up to him.

Jeff Sessions is a true believer in Trump’s policy agenda. But he hasn’t been a lawless crony.

Back in February 2016, Jeff Sessions took a major risk by becoming the first United States senator to endorse Donald Trump’s presidential campaign. It made a great deal of sense — Sessions had devoted much of his political career to, essentially, the agenda Trump was campaigning on. He was the Senate’s leading critic of both legal and illegal immigration, he’d blasted trade deals he thought were unfair, and he wanted to empower law enforcement to be “tougher” on crime.

And when Trump won, it appeared the risk had paid off. Sessions was rewarded with the attorney general appointment, and once confirmed, he set about implementing the policy agenda that he by all accounts deeply believes the country needs. As Dara Lind writes, he’s instructed US attorneys to more aggressively charge drug and immigration offenses, expanded police powers to take property from people who haven’t yet been convicted of crimes, and killed Justice Department initiatives to oversee local police departments accused of racial discrimination.

As sweeping as Sessions’s changes have been, though, it’s important to keep in mind that they’ve been policy changes.

At one point, it seemed worryingly possible that a Trump administration Justice Department could be very different — that it could be essentially remade to serve the personal whims and persecute the political opponents of Donald Trump.

Past presidents have long used Justice Department appointments to steer policy in the general direction they prefer, by prioritizing resources for certain issues, using general prosecutorial guidelines, and so on.

But the idea of a president specifically telling the Justice Department which particular people and matters they should investigate — especially if political rivals are involved — seemed beyond the pale of American politics.

Yet on the campaign trail, Trump used a great deal of illiberal rhetoric that raised alarm bells about potential authoritarianism. He repeatedly, for instance, called for his main rival Hillary Clinton to be locked up and promised that he’d ask the Justice Department to appoint a special prosecutor to look into her activities. And though Trump changed his tune on this after the election, his appointment of a close campaign ally as attorney general raised questions about how independent the Justice Department would be.

But Sessions put minds at ease by choosing Rod Rosenstein, a longtime US attorney with a good reputation in Washington’s legal community, as his deputy. And his Justice Department so far seems to have ignored Trump’s tweeted rants about whom and what they should be investigating.

Most crucially of all, once in office, Sessions did in fact choose to recuse himself from oversight of the Russia investigation and all investigations related to the campaign back in March (though only after news stories about undisclosed contacts he had with the Russian ambassador gave him a bit of a push).

Sessions’s recusal from the Russia investigation infuriated Trump — and led to a remarkable public tongue-lashing from the president

Trump immediately saw the potential import of Sessions’s recusal, and he was irate. The Washington Post’s Robert Costa reported the very weekend it happened that Trump left for a trip to Florida “in a fury ... fuming about Sessions’s recusal and telling aides that Sessions shouldn’t have recused himself.”

Sessions (and Rosenstein) then did Trump a favor by establishing a pretext for him to fire FBI Director James Comey in May, writing letters criticizing Comey’s handling of the Clinton email case, even though Trump himself admitted he wanted Comey gone because of his handling of the Russia investigation.

But after a week-long national uproar, Rosenstein, who is in charge of the Russia investigation due to Sessions’s recusal, appointed Robert Mueller to take over the probe as special counsel. “The public interest requires me to place this investigation under the authority of a person who exercises a degree of independence from the normal chain of command,” Rosenstein said.

As the investigation has proceeded (and dominated headlines) in the months since, Trump has been growing angrier and angrier about it — and he appears to be placing a great deal of blame on Sessions for its existence, because of his recusal.

Trump outright told the New York Times last week that if he knew Sessions would recuse himself from the Russia investigation, he “would have picked somebody else.” The recusal, Trump went on, was “extremely unfair, and that’s a mild word, to the president.” The obvious implication is that an attorney general who didn’t recuse himself could have better reined in Mueller.

Now, in a series of tweets this week, Trump has expanded the critique, referring to Sessions as “beleaguered” and complaining that he has “taken a VERY weak position on Hillary Clinton crimes.” Coupled with various leaks from administration sources that Trump is looking for a new attorney general, this sure seems to be an effort to either dog Sessions into quitting or lay out a public pretext for his firing.

But this isn’t just about Sessions. It’s about whether Trump can turn the Justice Department away from his allies and against his opponents.

Yet lurking behind all this is one crucial fact: If Sessions is fired or quits, Trump would be able to appoint a new attorney general who would not be recused from the Russia investigation. This would mean, essentially, a Trump ally seizing control of the investigation back from Rosenstein, whom the president doesn’t know well or trust.

Theoretically, a new and un-recused attorney general could let Mueller’s investigation proceed without interference until the final decision of whether to file charges is made. But many Trump allies view pushing out Sessions as part of a larger strategy to shut down Mueller’s investigation completely, according to the Washington Post’s Sari Horwitz, Matt Zapotosky, and Robert Costa.

It would, of course, be outrageous if the president of the United States fired enough people that an investigation into himself and his associates could be shut down. It would mean a political crisis that we haven’t seen since Watergate, and even one that’s potentially worse than Watergate (since President Nixon did allow a new special prosecutor to be appointed after he fired the first one, after all).

And then there’s the not-at-all-small matter of the president of the United States tweeting, again and again in recent months, that he wants leading Democrats like Hillary Clinton and Barack Obama to be investigated for supposed crimes:

Actors throughout the political system tend to roll their eyes at Trump’s tweets on these topics and not take them too seriously. And arguably, that’s been the right approach so far — six months in, President Trump has not been able to bend the federal government to his will on these matters.

And yet we are only six months in. A purge of the Justice Department’s top leadership could certainly change things.

It’s tough to imagine a modern United States federal government that goes about deliberately trying to lock up the president’s political opponents. But according to Trump’s own words, that is what he is imagining and actively wants to happen. The president has made it crystal clear that he has little respect for the rule of law and for democratic norms, and it’s time to take this danger seriously.

What happens if Sessions is out?

If Sessions is fired or quits in the coming days, the stakes for the Justice Department — and for the Trump presidency — would be immensely high.

On a policy level, of course, immigration critics would have lost one of their most fervent allies in the administration, throwing the future of federal policy affecting millions of lives into question. Canning Sessions could also cost Trump some support among conservatives who have long viewed the attorney general as a more reliable policy ally than the president, as this critical article on Breitbart News and this Jim DeMint statement suggest.

And then concerns about the rule of law and the future of both the Mueller investigation and the Justice Department itself would come to the forefront as Trump selects a replacement for Sessions.

President Trump has said that he wants an attorney general who wouldn’t recuse himself from the Russia investigation. He’s said he wants the Justice Department to investigate Clinton and Democrats. It seems obvious that he would take these priorities into account when selecting Sessions’s replacement. It also seems obvious that he would want an attorney general who will bottle up or even actively shut down the Russia probe.

The one hurdle is that a replacement would need to be confirmed by the United States Senate.

Though Republicans control the majority, several Republican senators, like Lindsey Graham and Richard Shelby, have already made clear that they would not take Sessions’s ouster kindly. Others, like John McCain, have made clear that they want a full investigation of the Russia scandal. Any three GOP defections could kill any Trump nominee (if Democrats unite in opposition to him or her).

So finding someone who’s enough of a Trump crony to win Senate confirmation for this post could be very difficult. It’s such a challenge that rumors swirled this week that Trump would try and circumvent that process completely. There was chatter that Sessions could be fired while the Senate was on recess in August — and that Trump could use the president’s recess appointment power to appoint a replacement who could serve until early 2019. However, Senate Democrats reportedly plan to use procedural moves to prevent the chamber from officially recessing, which would block that from happening.

Still, there’s a serious risk here that a nominee with strong-on-paper credentials would skate through hearings giving vague or noncommittal answers — while President Trump has gotten different assurances of that nominee’s intentions in private.

Any Trump replacement for Sessions would need to be grilled, at length and under oath, about just what discussions he or she has had with the president and top administration aides. Any nominee should have to commit under oath to recuse himself or herself from the Russia investigation.

If the Senate confirms anyone who has not made that sworn promise, they risk letting the president get away with a potential cover-up and doing grave damage to the rule of law in the United States.