“Fake news!” roared Donald Trump, the work of “sick people.”

The president-elect was referring to a 35-page dossier of lurid details of his alleged sexual misconduct in Russia, worked up by a former British spy. A two-page summary of the 35 pages had been added to Trump’s briefing by the CIA and FBI — and then leaked to CNN.

This is “something that Nazi Germany would have done,” Trump said. Here, basically, is the story.

During the primaries, anti-Trump Republicans hired the ex-spy to do “oppo research” on Trump, i.e., to dig up dirt.

The spy contacted the Russians. They told him that Trump, at a Moscow hotel in 2013, had been engaged in depraved behavior, that they had the films to blackmail him, and that Trump’s aides had been colluding with them.

When Trump won the nomination, Democrats got the dossier and began shopping it around to the mainstream media. Some sought to substantiate the allegations. None could. So none of them published the charges.

In December, a British diplomat gave the dossier to Sen. John McCain, who personally turned it over to James Comey of the FBI.

On Jan. 7, Director of National Intelligence James Clapper and his colleagues at the NSA, CIA and FBI decided the new president needed to know about the dossier. They provided him with a two-page synopsis.

Once CNN learned Trump had been briefed, the cable news network reported on the unpublished dossier, without going into the lurid details.

BuzzFeed released all 35 pages. The story exploded.

Besides Trump’s understandable outrage, his Jan. 11 press conference produced related news.

U.S. intelligence agencies had for months contended that it was Russia who hacked the DNC emails and those of Clinton campaign chief John Podesta. Putin’s objectives, they contend, were to damage both U.S. democracy and Hillary Clinton, whom Putin detests, and to aid Trump.

Trump had previously dismissed claims of Russian hacking as unproved conjecture, and also as being advanced to delegitimize his victory.

Wednesday, Trump conceded Russia did it: “As far as hacking, I think it was Russia,” adding, Vladimir Putin “should not be doing it.”

The stakes in all of this are becoming huge.

Clearly, Trump hopes to work out with Putin the kind of detente that President Nixon achieved with Leonid Brezhnev.

This should not be impossible. For, unlike the 1970s, there is no Soviet Empire stretching from Havana to Hanoi, no Warsaw Pact dominating Central Europe, no Communist ideology steering Moscow into constant Cold War conflict with the West.

Russia is a great power with great power interests. But she does not seek to restore a global empire or remake the world in her image. U.S.-Russian relations are thus ripe for change.

But any such hope is now suddenly impaired.

The howls of indignation from Democrats and the media — that Trump’s victory and Clinton’s defeat were due to Putin’s involvement in our election — have begun to limit Trump’s freedom of action in dealing with Russia. And they are beginning to strengthen the hand of the Russophobes and the Putin-is-Hitler crowd in both parties.

When Secretary of State-designate Rex Tillerson went before the Foreign Relations Committee, Sen. Marco Rubio demanded to know why he would not publicly declare Putin a “war criminal.”

The more toxic Putin-haters can make the Russian president, the more difficult for President Trump to deal with him, even if that is in the vital national interest of the United States.

The sort of investigation for which McCain has been clamoring, and the Beltway drums have now begun to beat, could make it almost impossible for President Trump to work with President Putin.

The Washington Post describes the engine it wishes to see built:

“The investigators of Russian meddling, whether a Congressional select committee or an independent commission, should have bipartisan balance, full subpoena authority, no time limit and a commitment to make public as much as possible of what they find.”

What the Post seeks is a Watergate Committee like the one that investigated the Nixon White House, or a commission like the ones that investigated 9/11 and the JFK assassination.

Trump “should recognize,” writes the Post, “that the credibility of his denials of any Russian connections is undermined by his refusal to release tax returns and business records.”

In short, when the investigation begins, Trump must produce the evidence to establish his innocence. Else, he is Putin’s man.

This city is salivating over another Watergate, another broken president. But President-elect Trump should be aware of what is at stake. As the Wall Street Journal writes:

“Mr. Trump’s vehement denials (of collusion with Moscow and corrupt behavior) also mean that if we learn in the future that Russia does have compromising details about him, his Presidency could be over.”

Yes, indeed, very big stakes.