The biggest issue in American politics right now is something called “the Nunes memo.”

The four-page document, prepared by Rep. Devin Nunes (R-CA), alleges serious abuses of power by the FBI during its investigation into the Trump campaign’s ties to Russia. House Republicans and conservative media have cast it as proof of President Donald Trump’s long-running allegations of FBI bias against him; Democrats say it’s deeply misleading, twisting and cherry-picking classified intelligence to make the president seem right.

The memo was finally released to the public on Friday afternoon, four days after House Republicans voted to release it. It focuses almost entirely on FBI surveillance of one Trump campaign adviser, Carter Page, and is very thin on evidence of actual wrongdoing by the FBI.

Nonetheless, its release still threatens special counsel Robert Mueller’s Trump-Russia investigation. The document could be used as an excuse by President Trump, who authorized the memo’s release, to clean house at the Department of Justice — firing top officials he perceives as insufficiently loyal, like Deputy Attorney General Rod Rosenstein. Trump did tweet something ominous just a few hours before the memo was released to the public:

The top Leadership and Investigators of the FBI and the Justice Department have politicized the sacred investigative process in favor of Democrats and against Republicans - something which would have been unthinkable just a short time ago. Rank & File are great people! — Donald J. Trump (@realDonaldTrump) February 2, 2018

Ultimately, the document raises the question: Is there an anti-Trump bias at the FBI, and if so, does it justify placing the historically independent bureau under Trump’s personal control? It’s a question with profound implications for the health of American democracy, and one that explains why the memo became such a source of controversy.

What follows is a guide to the biggest questions swirling around the Nunes memo.

1) Who is Devin Nunes, and why did he prepare this memo?

Devin Nunes is the chair of the House Intelligence Committee and a longtime Trump ally. He served on Trump’s transition team after the election and defended former national security adviser Michael Flynn when he was (credibly, it turns out) accused of lying about his contacts with Russia last February.

Nunes “seemed to go out of his way to defend Trump,” the Washington Post’s Aaron Blake wrote, “in a way few others did.”

Perhaps the clearest example arose after Trump tweeted in March that President Obama had “wiretapped” Trump Tower during the 2016 presidential campaign. The heads of both the NSA and the FBI categorically denied that any such wiretapping had occurred. But Nunes quickly came to Trump’s defense, holding a press conference to announce that “the intelligence community incidentally collected information about US citizens involved in the Trump transition.”

What this actually meant is that some Trump transition personnel had been in contact with foreigners legally under surveillance, and their conversations were intercepted as part of that surveillance (that’s what “incidentally collected” means). This, needless to say, did not justify Trump’s claim that the Obama administration was spying on his campaign headquarters.

However, the timing of Nunes’s press conference and the confusing way in which Nunes presented the information made it seem like he was trying to provide cover for Trump. The president himself said Nunes’s revelation “somewhat” vindicated his tweets.

Then it turned out that Nunes got his information from the Trump White House itself. Ezra Cohen-Watnick, the National Security Council’s senior director for intelligence, uncovered the information; Michael Ellis, a White House attorney who worked for Nunes prior to the Trump administration, personally took it to Nunes.

To recap: Nunes released information in such a manner as to make it look like Trump’s claims of being persecuted by law enforcement were true — and did so after secretly getting the information from the Trump White House. The situation proved to be such an embarrassment that Nunes was forced to recuse himself from the intelligence committee’s investigation into Russia for eight months during a House ethics investigation into his conduct.

So when news broke in mid-January that Nunes had been working in secret to prepare a memo on FBI surveillance of the Trump campaign, the initial sense among intelligence experts was that it would be a repeat of the wiretapping debacle — Nunes misrepresenting intelligence to support President Trump’s political position.

But many of Nunes’s colleagues in the House saw it as damning proof of anti-Trump animus at the FBI. They started a public campaign, backed by conservative media, to #ReleaseTheMemo. This culminated in Friday’s release.

2) What does the Nunes memo allege?

The memo focuses on surveillance of Carter Page, a Trump campaign foreign policy adviser with business ties to Russia and open sympathies with the Kremlin’s foreign policy. The key allegation is that the surveillance of Page was improperly authorized — and potentially politically motivated.

In July 2016, while advising the Trump campaign, Page flew to Moscow and met with Russian officials. This raised eyebrows among US intelligence officers, to say the least. So the FBI and DOJ put together an application to a Foreign Intelligence Surveillance Act (FISA) court — a court that approves surveillance warrants pertaining to national security and foreign intelligence — to start watching Page. The court granted the application.

The Nunes memo alleges that this surveillance was not properly vetted by the court; specifically, that it relied on the now-infamous Steele dossier, the document prepared by former British spy Christopher Steele alleging the existence of a conspiracy between Donald Trump and the Russian government. Steele’s research was, partially and indirectly, financed by the Clinton campaign — which the memo alleges is a major problem.

The Steele dossier, Nunes writes in the memo, “formed an essential part of the Carter Page application.” Nunes goes on to suggest that the application omitted several key facts about the Steele dossier that undermine its credibility, the most notable being the dossier’s financial backing from Democrats, and that Steele himself expressed opposition to Donald Trump becoming president.

There are lots of problems with the memo’s line of reasoning. For one thing, Steele is a respected investigator, and some of his dossier’s less explosive allegations have so far proven to be true. The FBI’s surveillance application may have relied on Steele’s findings, but if that’s true, it doesn’t necessarily discredit the application.

The memo’s claims are also impossible to evaluate without seeing the underlying intelligence it was based on. Nunes could have highlighted the FBI’s citation of Steele without mentioning other, more concrete sources the agency listed.

Moreover, the FBI relies on sources with axes to grind all the time — people typically don’t go to the authorities with damaging information about people they like. The key question in an application like this isn’t whether the source liked the target; it’s whether the specific claims they’re making are credible. The memo doesn’t address this at all.

Perhaps most fundamentally, the memo doesn’t ever substantiate core assertions about political bias on the FBI’s part. The memo’s overall method of argument is to imply something suspicious without asserting malfeasance outright.

For example, the memo repeatedly notes that the DOJ knew that “political actors” were involved in the financing the Steele dossier. It implies that the FBI knew they were Democrats and chose to ignore it.

But that’s never clearly stated, and for good reason. The firm that employed Steele was initially contracted by a conservative publication, the Washington Free Beacon, not any Democrats or Democratic political campaign. It’s possible the FBI knew of the Free Beacon’s involvement or was aware that some political actor was involved in funding it — but didn’t know about the Clinton campaign’s involvement. The memo never clarifies which “political actors” it means.

This is why the early assessment from intelligence experts is that there isn’t really a lot of there there.

“If this is their evidence of ‘Worse than Watergate,’ it’s thin,” Julian Sanchez, an expert on surveillance at the libertarian Cato Institute, writes. “This reads like something you’d put together to *sound* scandalous to someone who isn’t going to parse it closely.”

3) Does the Nunes memo implicate anyone important?

The memo isn’t just about the initial FISA application. FISA warrants on Americans, like Page, expire after 90 days — which means the Bureau needs to petition for a renewal every 90 days if they want to keep snooping on a target.

This happened repeatedly with Page. One of those renewals was signed off on by Deputy Attorney General Rod Rosenstein — the man currently supervising special counsel Robert Mueller’s Russia investigation.

Rosenstein is only mentioned once in the memo — he’s one of several officials who signed off on renewing the Page warrant. But his inclusion is especially important. “Republicans,” the New York Times speculates, “could potentially use Mr. Rosenstein’s decision to approve the renewal to suggest that he failed to properly vet a highly sensitive application for a warrant to spy on Mr. Page.”

But it’s actually deeper than that.

The memo somewhat implies that the Russia investigation is a corrupt partisan hatchet job. By bringing Rosenstein into it, it also ends up indicting the man currently in charge of the Russia investigation — suggesting he’s at best incompetent and at worst corrupt. Theoretically, this would provide cause for Trump to dismiss Rosenstein.

Trump currently can’t fire Mueller without Rosenstein’s approval and Rosenstein said in December that there is no “good cause” to fire Mueller. If the president were to fire Rosenstein based on the memo, he might eventually be able to dismiss Mueller.

There isn’t a lot of support for such a firing in the memo. Typically, FISA warrants only get renewed if they uncover new evidence that justifies continuing the surveillance. It seems plausible that this could have happened with Page, given his Russian connections. In 2013, for example, Russian agents approached him with the intent of turning him into an asset (a point the Nunes memo never notes).

This, experts say, is almost certainly what happened.

“It’s [the FISA application] reapproved if you have new information justifying the original probable cause and the government’s need to listen,” writes Asha Rangappa, a former FBI special agent and current Yale lecturer, suggesting the memo actually shows that the government had good cause to surveil page.

So if Trump wants to fire Rosenstein based on one line in the Nunes memo, it would be quite a stretch.

4) Why did House Republicans want to release the memo so much?

Ostensibly, Republicans in the House pushed to release the memo because they believe it outlines surveillance abuses the American people need to know about.

“Let’s have a great debate about its consequences and the opportunity it presents to make things better, so these things never happen again,” Rep. Matt Gaetz (R-FL) said in a January 30 speech on the House floor.

But experts on the FISA system, even civil libertarians critical of the way law enforcement uses it, note that these Republicans aren’t proposing any changes to how FISA works, or even suggesting that the system in general needs reform to stop any future abuses.

“There’s a conspicuous lack of interest in drawing any policy conclusions from what they purportedly consider a major institutional scandal,” said Sanchez, the Cato expert.

Instead, the motivation for the push to release the memo seemed purely political. Many of the most vigorous supporters of #ReleaseTheMemo, like Gaetz, have also called on President Trump to get rid of Robert Mueller. “I think the president should’ve fired Mueller long ago,” Gaetz said in a December interview with Vox.

These are people who seem to either genuinely believe that the Russia investigation is a partisan witch hunt targeting the president or believe there’s some political advantage to be gained from championing an anti-FBI crusade near and dear to both the president’s and Fox News’s heart.

Either way, experts say the motivation behind the memo’s release seems pretty clear — it’s a way of waging war on the Russia investigation specifically and the FBI in general.

“The release of the memo, and the fabrication of a set of ideas around the memo, empowers Trump to go after the FBI,” Ryan Goodman, a former Defense Department special counsel and current editor of Just Security, said. “The ultimate goal is undermining the Mueller investigation. There doesn’t seem to be another reason for the president to be so obsessed with Rod Rosenstein and to be gunning for him.”

5) Why did the FBI and Democrats oppose it?

The FBI and Democrats don’t like the Nunes memo for one big reason: They think it’s full of lies.

On Wednesday, the FBI put out a strongly worded statement signaling the agency’s worry with the memo’s accuracy:

The FBI takes seriously its obligations to the FISA Court and its compliance with procedures overseen by career professionals in the Department of Justice and the FBI. We are committed to working with the appropriate oversight entities to ensure the continuing integrity of the FISA process. With regard to the House Intelligence Committee’s memorandum, the FBI was provided a limited opportunity to review this memo the day before the committee voted to release it. As expressed during our initial review, we have grave concerns about material omissions of fact that fundamentally impact the memo’s accuracy.

Rep. Adam Schiff (D-CA), the top Democrat on the House Select Intelligence Committee, said after the statement that he sided with the FBI. “I think the FBI is exactly right. I have the same grave concerns over it.” He added that he knew of the FBI’s concerns before he voted against the memo’s release.

Schiff and his fellow Democrats on the committee also went the extra step of compiling a 10-page memo of their own. It reportedly asserts two things: First, that the FBI didn’t abuse its FISA power when requesting the Page warrant, and second —more importantly — that the Nunes memo is simply an effort to help the White House discredit the Mueller probe.

On Monday, Rep. Mike Quigley (D-IL) asked Nunes if his staffers worked with the White House on his memo. Nunes originally answered the question by saying “as far as I know,” no one collaborated with the White House. Ultimately, though, he refused to answer the question — perhaps suggesting that there may actually have been some collusion there.

The House Intelligence Committee, however, voted not to make the Democratic memo public on Monday. There have been no moves towards releasing it since.

6) Why did Trump approve releasing the Nunes memo?

Trump didn’t offer a clear public explanation. But based on other things he’s said, the reason seems clear: He has publicly stated several times that the Trump-Russia probe is a “witch hunt” perpetrated by rogue partisans within the FBI. The memo, he and his allies on the Hill believe, support this position.

“Trump is shockingly overt about believing that the problem here is that the FBI is staffed by loyalists to the wrong person,” Sanchez said. “He does, in fact, seem to think that the job of the DOJ, and the FBI, and the rest of the intelligence community is to protect the president and follow his orders — including going after his political enemies based on stuff he saw on Fox News, if that’s what he wants to do.”

Ironically, the memo concludes on a note that actually could vindicate the broader Russia investigation.

The last paragraph of the memo is all about the FISA application’s references to George Papadopoulos. The Trump campaign foreign policy adviser also had connections with Russia — he had been approached by a Russian-linked professor in London in the spring of 2016 who told him the Kremlin had dirt on Hillary Clinton.

The memo admits, crucially, that the Trump-Russia investigation originated with Papadopoulos’s misbehavior, not Page’s. “The Papadopoulos information,” the memo says, “triggered the opening of an FBI counterintelligence investigation in late July 2016.”

This shows that even if the Carter Page FISA application were flawed, the Trump-Russia investigation had another foundation — evidence about Papadopoulos’s Russian contacts. That means you can’t discredit the entire Russia investigation by pointing to the Page warrant.

The memo tries to insinuate that this too was biased against Trump — noting that one of the FBI agents handling the Papadopoulos situation, Peter Strzok, had sent some text messages critical of Trump to his “mistress,” FBI attorney Lisa Page. But at this point, we know that the information on Papadopoulos was true — because he pled guilty to lying to the FBI and gave a ton of information to special counsel Robert Mueller’s office.

So if this is an attempt to buttress Trump’s campaign against the Russia investigation, as his past behavior would suggest, it’s not an especially successful one.

7) What happens now that the memo has been released?

The issue now moves beyond the realm of fact and into politics. The question isn’t so much what the Nunes memo says, but how those findings are interpreted by various different political actors.

The many holes in the Nunes memo’s reasoning and evidence could end up undermining the case against the Russia probe. Worse, the fallout of the release could lead to more leaks proving that Nunes’s account is wrong. In that scenario, it would end up as an unforced error.

But it’s also possible that this gets coded in entirely partisan terms — with conservatives and Republicans seeing the memo as damning and it leading to a renewed assault on the FBI and the Mueller probe. Some conservatives are already taking Nunes’s memo at face value and lambasting the FBI as a partisan, anti-Trump agency.

Since Republicans control the majority in both Houses of Congress, their reaction in the next few days is vital. It’s still too early to tell just what that’ll be.

8) Does this threaten the Mueller probe?

Possibly.

The campaign to release the memo was part of a much larger conservative effort to discredit the Mueller investigation. Its release could end up serving as pretext for removing those responsible for the Mueller probe.

According to the Washington Post, Trump told his close advisers prior to the memo’s release that it could give him the ammo he needs to fire Rosenstein or force him to resign. Trump could replace Rosenstein with someone friendlier to the Trump administration and more willing to constrain Mueller. That could prove more detrimental to the Mueller probe in the long run.

Rangappa, the Yale expert, writes that the deputy attorney general could effectively cripple the Mueller investigation by rejecting Mueller’s requests to investigate more people, obtain new evidence, or pursue charges against additional people, for instance. More simply, the new appointee could just fire Mueller.

Again, this is more of a political game than a legal one. Nunes and many conservatives say there’s proof in the memo that the FBI is corrupt, and the FBI and Democrats say this is all a smokescreen to protect the president.

So what’s likely to happen in the coming days is escalating conflict between House Republicans and Trump administration officials who want the president to fire Rosenstein and shut down the Russia probe, and the FBI and Democrats who oppose all of this.

9) How bad could the memo fallout get?

There are two broad ways an extended political war between the FBI and Trump and his allies could go. In the first, the FBI is brought to heel, and Rosenstein and other senior FBI executives are fired and replaced with more Trump-friendly appointees. The Mueller investigation is quashed, and the bureau essentially serves more like an arm of the Trump administration than as a quasi-independent agency.

The implications of this scenario for American democracy are pretty scary.

“I shudder to think what the [2020] election looks like when you’ve got a guy who says, ‘I saw Fox & Friends this morning and my opponent is a crook’ ... except now you’ve got an FBI and a DOJ that say, ‘Yes, sir,’” says Sanchez.

In the second scenario, the memo leads to a lot of FBI-Republican skirmishing but no actual showdown. Trump either decides not to fire Rosenstein or is somehow stopped from doing so, the Mueller investigation continues unhampered, and the FBI remains relatively untainted by political influence.

There are many factors that could determine which of these two outcomes plays out. Two of the key ones are congressional Republicans, particularly Senate Republicans, and Trump’s own staff.

Senate Republicans have been notably quieter and more restrained about attacking the FBI than their peers in the House. Senate Republicans also have to confirm Trump appointees to the Justice Department; they could make clear that if he fires Rosenstein/Mueller and tries to appoint a crony to take their place, they won’t confirm whomever he picks.

What influential Senate Republicans say and do in the days after the memo’s release, in short, could signal to Trump whether he has enough backing to really take on the FBI.

“This particular president advances when he senses weakness,” Goodman said. “The critical factor is the will of many Republicans to stand up.”

There are some encouraging signs on this front. Sen. John McCain (R-AZ), for example, responded to the memo with a condemnation of the entire campaign to undermine the DOJ and FBI. “The latest attacks on the FBI and Department of Justice serve no American interests — no party’s, no president’s, only Putin’s,” he wrote.

Members of Trump’s White House are also an important check, having blocked his moves to interfere with the Mueller probe in the past.

The New York Times reports that in June, Trump ordered White House counsel Don McGahn to fire Mueller. McGahn said he’d rather resign than do that, and Trump backed down. He was, according to the Times, “concerned that firing the special counsel would incite more questions about whether the White House was trying to obstruct the Russia investigation.”

If McGahn and other voices of relative restraint in the White House succeed in constraining the president’s impulse to act, or even refuse to carry out his orders, then it’s possible that the whole memo mess will amount to little in the end.