If true, it’s a bombshell for Robert Mueller’s investigation and a potential game-changer for Donald Trump. But … is it true? And if so, what are the ramifications of Michael Cohen’s potential testimony that Trump knew in advance of the meeting in the Trump Tower with Russians in an effort to dig up dirt on Hillary Clinton?

We may be about to find out, according to CNN:

Michael Cohen, President Donald Trump’s former personal attorney, claims that then-candidate Trump knew in advance about the June 2016 meeting in Trump Tower in which Russians were expected to offer his campaign dirt on Hillary Clinton, sources with knowledge tell CNN. Cohen is willing to make that assertion to special counsel Robert Mueller, the sources said.

Cohen’s claim would contradict repeated denials by Trump, Donald Trump Jr., their lawyers and other administration officials who have said that the President knew nothing about the Trump Tower meeting until he was approached about it by The New York Times in July 2017.

Cohen alleges that he was present, along with several others, when Trump was informed of the Russians’ offer by Trump Jr. By Cohen’s account, Trump approved going ahead with the meeting with the Russians, according to sources.

There are a couple of problems with this development, however. First off, the attorney who liked taping important conversations has no independent corroboration for this claim:

To be clear, these sources said Cohen does not have evidence, such as audio recordings, to corroborate his claim, but he is willing to attest to his account.

Second, as Jim Sciutto reported last night, Cohen never mentioned this in his congressional testimony. If Cohen said something even hinting at this, Democrats would have highlighted it in their minority reports and shouted it from the rooftops — it’s that big of a smoking gun. Regardless of whether the panel had Cohen take an oath or not, lying or deliberately omitting material information in congressional testimony is a crime. That puts Cohen in a position of having to explain what amounts to perjury if and when Robert Mueller puts him on the stand as a witness. It’s not impossible to use a witness under such circumstances, but it’s far from ideal — and it would at least require some corroborating evidence or testimony. And if Mueller had the latter, he wouldn’t need Cohen anyway.

But let’s say that CNN’s right on this story and Cohen’s telling the truth. What would be the ramifications? For starters, Cohen wouldn’t be the only person looking at perjury issues:

After reports of the meeting first surfaced last year, Trump Jr. claimed that only Russian adoption policy was discussed. He also testified to the Senate Judiciary Committee last September that he didn’t inform his father about the meeting, according to a transcript released by the panel.

The president himself, when asked about the meeting, told reporters aboard Air Force One last July, “I only heard about it two or three days ago.” That same month, Jay Sekulow, a member of Trump’s legal team, said: “The president wasn’t aware of the meeting, did not participate in the meeting, did not attend the meeting.”

If Cohen’s telling the truth now, Don Jr would certainly face legal consequences for false testimony, especially if he told the same story to investigators. However, it’s not clear whether Trump himself would have the same issues. Don’t forget that he hasn’t been interviewed by investigators yet; he’s made statements to the press, but that doesn;t create the kind of legal jeopardy that can lead to indictments. It would undermine Trump’s political credibility, and that would certainly matter next year, but it’s not likely to lead directly to prosecutable liability. Whether or not Congress decided to take it up as an impeachment issue is another matter, though, and this issue has already raised talk of impeachment anyway. As Chris Cuomo says, this raises the Watergate question: what did the president know, and when did he know it?

But all this assumes CNN’s correct and Cohen’s telling the truth. It seems somewhat strange that Cohen, who taped conversations with his meal-ticket client about payoffs to paramours, didn’t turn on the recorder when it came time for Trump to allegedly approve a meeting with Russian interlocutors in the middle of the campaign. Furthermore, it’s clear that Cohen is in deep legal trouble at the moment, and has been campaigning through his new attorney Lanny Davis for some sort of deal. This is literally the only thing Cohen has left to trade for his freedom.

One last point: don’t forget that Mueller cut Cohen loose months ago. He’s being investigated by the Department of Justice in the Southern District of New York, not the special counsel office. If Mueller thought Cohen had this kind of information, would he have handed off the case? This looks like a Hail Mary to get Mueller’s attention and a deal, especially with the leak to a news agency. If Cohen had something usable on Trump, the first thing we would have heard was a transfer of the case back to Mueller, not a talking head debate on CNN about this claim.

What if you threw a credibility contest and everyone came in last?

Addendum: Trump adamantly denied the allegation on his favorite platform: