It’s too early to say how, exactly, Robert Mueller’s special-counsel investigation of Russiagate will end. Sometimes, amid the flow of revelations—that Mueller has impaneled at least two grand juries, that he’s issuing a stream of subpoenas, that’s he’s executed search warrants and a pre-dawn raid, that his team has met with the author of the controversial “Steele dossier”—it’s possible to get lost in the currents.

Yet Mueller is on a collision course with Donald Trump, and it’s one that could have nation-rocking constitutional, legal, and political consequences. Like Watergate four decades ago, Russiagate could bring down the president. Unlike Watergate, however, the Mueller inquest is taking place in a country far more bitterly divided than Richard Nixon’s America. There’s no way to predict how Trump’s hard-core supporters, from alienated, angry white men to members of the National Rifle Association to outright neo-Nazis and KKK types, might react if Trump is impeached. Yet Mueller—quiet, relentless, implacable—seems to be willing to let the chips fall where they may.

There are many paths the Mueller investigation might take as it gets closer to its end game. (It should be noted that if there’s any timetable for Mueller to complete his work, no one knows what it is, and Mueller himself is unlikely to listen to pro-Trump Republicans telling him to hurry up.) What’s certain, however, is that every time Trump alienates another member of Congress, as with his recent tweet-storm aimed at Tennessee Senator Bob Corker, he alienates the very people on Capitol Hill he’s going to need in his corner should Mueller deliver a scathing report. Indeed, it should worry Trump’s lawyers no end if it’s true that, as the Los Angeles Times reports, “Corker is saying what other Republicans will only whisper about President Trump,” and that Corker’s belief that at best Trump’s aides have to “contain him” in “an adult daycare center” is also believed privately by many other senators in the Republican caucus. As Gerald Seib put it in The Wall Street Journal, Trump is a “president without a party.”

So what’s likely to emerge from the special counsel’s work? “I don’t think that Mueller would recommend impeachment,” says Alan Morrison, a veteran constitutional lawyer and dean for public-interest and public-service law at the George Washington University Law School. “That’s not his job,” Morrison tells The Nation. “Impeachment is a different process, with a different set of standards.” While it depends on what he comes up with, Morrison says, Mueller will probably issue a report outlining his findings and let Congress sort out the results.

In that case, the focus shifts from law to politics. Because the Republicans control the House, impeachment—even should concrete evidence emerge of wrongdoing by Trump, including collusion with Russia’s meddling in the election or a clear case of obstruction of justice—could be a steep, uphill climb. A few dozen Republicans in the House would have to join Democrats to send Trump’s impeachment over to the Senate for a trial. Yet with the political clamor that a scathing Mueller report would trigger—and given Trump’s declining support among his own party—it’s not impossible that the House would vote to impeach.

Now it’s looking more and more likely that charges of obstruction could be filed. A just-released, 108-page study by the Brookings Institution concluded that “substantial evidence” already exists that “the president has likely obstructed justice.”

Adding to the uncertainty is the question of when Mueller will issue his report. The closer it occurs to the November 2018 midterm elections, the more political it becomes. Suppose his report concludes that Trump and/or his aides, advisers, and members of his family did encourage or support Russia’s 2016 actions. Would GOP members of Congress want to block impeachment proceedings on the eve of a potential Democratic wave? It would present them with an impossible dilemma: alienate the hard-core Trump base by voting to impeach, or energize a Democratic avalanche at the polls by siding with Trump over Mueller? If Democrats win back the House next year, a Trump impeachment in 2019—assuming, again, a damning Mueller report—becomes much more likely.

It’s been the subject of wide speculation that, as he digs into Russiagate, Mueller might issue criminal indictments of one or more current or former aides to Trump, or use the threat of such indictments to get his targets to testify against the president or others in exchange for immunity or a lesser charge. The two leading candidates for such treatment seem to be Gen. Michael Flynn, the former national-security adviser, and Paul Manafort, Trump’s 2016 campaign manager—but there could be others that fall into that category, too. The hardest nuts to crack, says Morrison, would be the president’s own family. “There are other people who know a great deal, such as the rest of his family, but depending on what they have against Donald and Ivanka and Jared, they would probably stand up for their father,” says Morrison.

Trump, of course, has options of his own. Faced with a deepening inquiry, growing opposition inside his own party, and uncertain support even among those who voted for him, he could resign. That’s not beyond imagining, since the playboy mogul can’t be enjoying being cooped up in the White House under the watchful eye of Gen. John Kelly, his chief of staff. Or Trump could look for ways to get rid of Mueller, just as he ousted FBI Director James Comey in May. That’s more difficult than it sounds, since Trump would have to convince a senior Justice Department official to do the deed. That could lead to a domino effect, a Saturday Night Massacre–like series of resignations until someone in DOJ’s food chain agrees to fire Mueller. Or, legal analysts tell The Nation, Trump might seek to abolish the Office of Special Counsel itself, eliminating the regulations that underpin Mueller’s work and shutting down the whole operation.

But firing Mueller would itself lead to a political firestorm, and numerous Republicans seem to cringe at the idea. As reported earlier in this column, several senators, both Democratic and Republican, have introduced legislation to make it harder for Trump to fire him. On September 26 the Senate Judiciary Committee held a hearing under the title “Special Counsels and the Separation of Powers,” which heard testimony from a range of legal experts and scholars. “The President has said that he does not intend to fire the special counsel, and I think that he made the right decision,” said Senator Chuck Grassley, chairman of the committee, who convened the hearing. “The bills we will discuss today raise potential separation of powers concerns that I believe deserve the attention of the Committee and merit a full and respectful discussion,” he added.

If Trump were to fire Mueller, the response would go far beyond a polite discussion of the separation of powers. It would trigger outrage among the president’s opponents, dismay his remaining allies in Congress, and accelerate calls for impeachment.

How Trump ought to respond to the investigation is a matter of bitter debate among the president’s advisers and supporters. According to The New York Times, Trump’s legal team has largely decided that cooperation with Mueller, rather than resistance, is the best course at present. However, other reports note that Trump recently met with an influential group of loyalists who urged the president to attack Mueller “with abandon.”

There is also the question, Can Mueller indict the president himself? Legal opinion on that question is divided, says Morrison. During Watergate, the special prosecutor chose not to indict Nixon but rather to list him as an “unindicted co-conspirator,” while indicting several of Nixon’s senior aides. “The president’s Office of Legal Counsel has…taken the view that the president can’t be indicted while he’s in office, but he can be indicted once he leaves office,” Morrison tells The Nation. “The Watergate special prosecutor had a different view: that they could indict him, but that indicting him would so complicate everything else that they chose not to indict him, and made him an ‘unindicted co-conspirator.’ But it was a political decision.”

None of this means, of course, that we have nothing to do but let Mueller do his work. The more pressure that builds against Trump, from several direction at once, the better.

One option, already widely discussed, is to activate the Constitution’s 25th Amendment, which declares that a majority of a president’s cabinet can remove him or her from office by submitting a “written declaration that the President is unable to discharge the powers and duties of his office.” Politically, that’s a tough one, despite Trump’s erratic, often bizarre behavior. Six months ago, it seemed unthinkably remote, but now that Secretary of State Rex Tillerson has reportedly called Trump a “fucking moron,” and amid widespread reporting that senior US officials are struggling to contain Trump’s outbursts—even as Trump lurches along a “path to World War III,” according to Senator Corker—it’s a bit less far-fetched. Still, despite Representative Jackie Speier’s call in August “to invoke the 25th Amendment,” her colleague on the House Intelligence Committee, Representative Adam Schiff, said back then that it could only be invoked after “some kind of physical incapacitation or serious mental illness or a breakdown,” and he added, “We’re still far from concluding that’s the case.” Barring far more extreme behavior from Trump, it seems, for the vice president and the cabinet to act now is something that could occur only in response to extraordinary political pressure.

Another option is for Congress to impeach Trump even before Mueller’s report. Some experienced observers, such as Professor Allan Lichtman of American University, author of The Case for Impeachment, have urged that the House of Representatives open an impeachment investigation right away. Among the eight separate counts Lichtman cites, he includes “abuse of power,” “conflicts of interest,” and “Russian connections.” At the Lawfare blog, Jane Chong and Benjamin Wittes wrote in August, “It’s now time to begin a serious conversation about the impeachment and removal of President Trump by opening a formal impeachment inquiry.” And a few members of Congress, including Representative Brad Sherman and Representative Steve Cohen, already support impeachment. Like calls to invoke the 25th Amendment, impeachment seems extremely difficult now. But current calls for it can play a useful role in preparing the public for what may lie down the road.

It should be encouraging to those who believe in the rule of law that so few leaks have emerged from Mueller’s office. By the time his investigation and parallel inquiries by the House and Senate intelligence committees are complete, the public should have a much fuller understanding of what exactly Moscow’s role was in 2016. (Already, as reported here last week, the Senate Select Committee on Intelligence has largely reached a consensus supporting the conclusion of three key US intelligence agencies that Russia was responsible for a wide range of actions last year aimed at affecting the election.) But what only Mueller is likely to tell us is whether or not Team Trump, wittingly or unwittingly, was a co-conspirator in that and whether or not the president could be guilty of obstruction of justice.