Donald Trump has insisted for more than a year that Russians didn’t try to get him elected. Special Counsel Robert Mueller put an end to those claims on Friday, declaring definitively that they did.

A federal grand jury indicted 13 Russian nationals and a so-called “troll farm” in St. Petersburg on Friday for a broad campaign to sway the 2016 election in Trump’s favor. The indictment alleges that the operation was funded to the tune of $1.25 million a month by companies controlled by a Russian businessman close to the Kremlin.

The indictment means that Trump can no longer credibly cast doubt on alleged Russian election meddling. His own national security adviser said Saturday that the evidence was “incontrovertible.” And if he was still harboring dreams of firing U.S. Special Counsel Robert Mueller or Deputy Attorney General Rod Rosenstein, something many Republicans already have warned against, such a move may be politically impossible.

The White House seized on Rosenstein’s declaration that Friday’s indictment didn’t allege “that any American had any knowledge” of the Russian interference, declaring “NO COLLUSION” in a statement. But the special counsel is still probing whether Trump or his campaign colluded with the Russians, a person familiar with the matter said.

Russian Foreign Minister Sergei Lavrov, speaking in Munich on Saturday, said no facts back up the allegations Russia meddled in the vote. “Until we see the facts, everything else is blather,” Lavrov said at the Munich Security Conference. He cited comments by Vice President Mike Pence and other U.S. officials who said the allegations were baseless.

National Security Adviser H.R. McMaster, speaking on a panel at the same conference Saturday, rebuffed Lavrov.

“The evidence is now really incontrovertible and available in the public domain, whereas in the past it was difficult to attribute,” McMaster said.

The U.S. intelligence community’s previous assertions that Russia interfered in the election, based on classified evidence never revealed to the public, were easily dismissed by Trump and his allies. Now there are concrete charges that Russians defrauded the U.S. government, with memos and other evidence to back up the allegations.

Read more: Mueller Accuses Russians of Pro-Trump, Anti-Clinton Meddling

“It’s much harder for him to be able to impugn the integrity of sworn testimony in open court about the intention of the Russians to interfere in our elections,” said Michael Allen, managing director of Beacon Global Strategies, a group that advises clients on international, cyber and homeland security policy.

Trump seemed to recognize the changed landscape himself.

In a tweet, he acknowledged a Russian “anti-U.S. campaign,” and in the White House statement he called the country a “bad actor.” He has previously — and frequently — described allegations of Russian meddling in the election as “a hoax.”

Investigation Continues

His lawyers complimented Mueller in statements, though they used the past tense –“did” — to describe his work, suggesting optimism that the investigation has concluded.

It has not. Rosenstein, at his news conference, said nothing about future indictments.

Some even saw in the indictment new doubt about Trump’s presidency.

“The obvious conclusion is that Donald Trump’s election as president can no longer be considered legitimate,” said Anders Aslund, a resident senior fellow at the Atlantic Council who specializes in Russian economic policy.

Rosenstein said the indictment does not allege “that the charged conduct altered the outcome of the 2016 election.”

Aslund predicted a “deep freeze” on U.S.-Russian relations; none of the indicted Russians are in U.S. custody. Rosenstein said the U.S. would request their extradition.

Allen, a former adviser to President George W. Bush and House Intelligence Committee Republicans, said the indictment makes it harder for Trump to challenge the FBI, Justice Department and intelligence community, and gives Rosenstein “sort of a bulletproof vest” against being fired or undercut. Such moves now would look like punishment.

Allen and others said that to avoid being weakened, Trump should immediately stop publicly doubting the Russian election meddling. “It’s still not too late to pivot and say, ‘No one is more upset about this than I am and here’s what I’m going to do about it,”’ Allen said.

Trump’s Narrative

But Trump’s political stature is entwined with the narrative he has built that Mueller’s probe is a “witch hunt” precipitated by Democrats.

“No, Russia did not help me, that I can tell you,” Trump told supporters at an Alabama political rally in September. “Any Russians in the audience? I don’t see too many Russians.”

He’s also repeatedly cited personal assurances from Russian President Vladimir Putin in maintaining his skepticism.

“Every time he sees me, he says, ‘I didn’t do that,”’ Trump said after a November meeting with Putin in Vietnam. “And I believe — I really believe — that when he tells me that, he means it. I think he’s very insulted by it, if you want to know the truth.”

He can only regain credibility if he abandons such public naivete, said Steve Sestanovich, a senior fellow for Russian studies at the Council on Foreign Relations and a former State Department official.

“Trump has got to stop using that ‘he-says-he’s-innocent’ line about Putin,” Sestanovich said.