(CNN) For much of the past 20 months, President Donald Trump and his administration have insisted that, for all of the smoke surrounding his 2016 campaign, there was no fire. A lot of people in Trump's orbit engaging in conversations and relationships with Russian officials, but no evidence of collusion and certainly nothing that linked Donald Trump to any wrongdoing.

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That very well might have changed Thursday night, with this report from BuzzFeed

"President Donald Trump directed his longtime attorney Michael Cohen to lie to Congress about negotiations to build a Trump Tower in Moscow, according to two federal law enforcement officials involved in an investigation of the matter.

"Trump also supported a plan, set up by Cohen, to visit Russia during the presidential campaign, in order to personally meet President Vladimir Putin and jump-start the tower negotiations. 'Make it happen,' the sources said Trump told Cohen."

A day after the report published, Mueller's office disputed it as "not accurate."

"BuzzFeed's description of specific statements to the Special Counsel's Office, and characterization of documents and testimony obtained by this office, regarding Michael Cohen's Congressional testimony are not accurate," said special counsel spokesman Peter Carr in a statement.

It's highly unusual for the special counsel's office to provide a statement to the media -- outside of court filings and judicial hearings -- about any of its ongoing investigative activities.

The BuzzFeed story also claims that Cohen confirmed this information to special counsel Robert Mueller after "the special counsel's office learned about Trump's directive for Cohen to lie to Congress through interviews with multiple witnesses from the Trump Organization and internal company emails, text messages, and a cache of other documents."

It's hard to overstate what a big deal that is. No other major outlets have confirmed the BuzzFeed report. But if the BuzzFeed report is right, then the President of the United States directed an underling to lie under oath -- which is, in and of itself, a crime.

Don't take my word for it. Check out this exchange between Democratic Minnesota Sen. Amy Klobuchar and Attorney General nominee William Barr during his confirmation hearings earlier this week (hat tip to Washington Post's Jacqueline Alemany for flagging ):

Klobuchar: The President persuading a person to commit perjury would be obstruction, is that right?

Barr: Well, yes. Well, any person who persuades another to -- yeah."

Klobuchar: "You also said that a President or any person convincing a witness to change testimony would be obstruction, is that right?

Barr: Yes."

Which, well, that was sort of on point, no?

Ask yourself this: Why, if there was nothing worrisome or untoward about Trump's dealings with Russia, would he instruct Cohen to lie about the depth and breadth of the conversations between the Trumps and the Russians regarding a potential construction project in Moscow? You don't have to lie or cover up things that are no big deal, right?

And we know from Cohen that he not only lied to the special counsel's office about Trump Tower Moscow but did so because he believed the truthful details of how long the conversations with Russians over the project went on (until June 2016, according to Cohen) and the involvement of the Trump family (Cohen said he repeatedly briefed them on developments) might jeopardize the billionaire businessman's chance of winning the Republican presidential nomination.

The Trump response to all of this? To attack Cohen. "If you believe Cohen I can get you a great deal on the Brooklyn Bridge," Trump lawyer Rudy Giuliani told The New York Times' Maggie Haberman on Thursday night after the news broke.

On Friday, Giuliani added in a statement, "Any suggestion -- from any source -- that the President counseled Michael Cohen to lie is categorically false. Michael Cohen is a convicted criminal and a liar."

The problem for Giuliani is that the BuzzFeed report doesn't hinge on Cohen. It says that the special counsel unearthed the evidence that Trump had told Cohen to lie through "multiple witnesses from the Trump Organization and internal company emails, text messages, and a cache of other documents." Mueller's office only went to Cohen to confirm/admit he actually did it. The special counsel's office didn't get the information from Cohen. That fact makes Giuliani's claim that Cohen is a proven liar -- which he is! -- largely meaningless.

If the BuzzFeed report is true (and yes that remains an "if" since CNN has not corroborated the reporting), then the entire Russia conversation changes. As Barr helpfully noted earlier this week, the President telling someone who works for him to lie to Congress about an ongoing investigation is obstruction of justice. And obstruction of justice is a crime.

The question is where Mueller would go next, assuming he has the goods on Trump for obstruction. Giuliani has repeatedly insisted that Mueller's team has told the Trump lawyers that they believe they cannot indict a sitting president

"All they get to do is write a report," Giuliani told CNN's Dana Bash in May 2017. "They can't indict. At least they acknowledged that to us after some battling, they acknowledged that to us."

Let's assume that's true -- although to do that it means we take Giuliani's word for it, which, given his recent "no collusion" flip-flop , might be a dicey proposition. What that means is that Mueller's report will likely move through political channels rather than legal ones. So rather than an indictment, perhaps impeachment.

"If true -- and proof must be examined -- Congress must begin impeachment proceedings and Barr must refer, at a minimum, the relevant portions of material discovered by Mueller," tweeted former Attorney General Eric Holder . "This is a potential inflection point."

Democratic Sen. Sheldon Whitehouse agreed, tweeting , "If this is true, this is plain, slam-dunk, criminal obstruction of justice (18 U.S.C. 1505, 1512), subornation of perjury (18 U.S.C. 1622), conspiracy (18 U.S.C. 371) and likely aiding and abetting perjury (18 U.S.C. 2)."

The "if true" part is, of course, the key. BuzzFeed has put the credibility of its entire organization on the line here. To make an allegation that the President of the United States purposely obstructed justice in an investigation into Russia's attempts to interfere in a presidential election is a massive deal -- and the sort of thing that, if wrong, can do irreparable damage to a company's reputation.

But if the BuzzFeed article is right -- and one of the reporters who bylined the story insisted on CNN Friday morning that the information in the piece is "rock solid" and that the sourcing "goes beyond" the two sources cited -- then this is the smoking gun (or at least a smoking gun).

If Mueller has the goods -- as the BuzzFeed report suggests he does -- then it is very, very hard to see how impeachment proceedings won't be started in the House once the special counsel report comes out. Whether Trump is actually removed from office is a more political question that depends on how clear -- if at all -- Trump's culpability is in the Mueller report.

Make no mistake: This is a very big moment in an investigation seemingly stuffed full of them. And, for students of history, you'll remember that the first article of impeachment against then-President Richard Nixon was that he had obstructed justice by ordering others to lie. So, there's that.