President Trump has been on an absolute tear about the Mueller investigation, now even accusing the prosecutor of McCarthyism.

It had been hard to fathom why the president was escalating his rhetoric and accusing Robert Mueller of pressuring people to lie and ruining their lives.

But it's becoming more clear by the minute, first with Mueller's office accusing Paul Manafort of blowing up his plea deal through lies, and Michael Cohen pleading guilty yesterday to lying about a potential Trump project in Moscow.

The president yesterday unloaded on his former personal lawyer before leaving for the G-20 summit. He called Cohen "a weak person. What he's trying to do is get a reduced sentence. He's lying about a project everyone knew about."

Cohen may be hoping for leniency, but Mueller says he is now telling the truth. Cohen may not have had any choice but to plead in a Manhattan courtroom because the special counsel has evidence that he lied to Congress.

And keep in mind that this is Cohen's second guilty plea. In a case not handled by Mueller, he already admitted guilt to bank fraud involving his taxi business and admitted paying hush money to Stormy Daniels — which he claims was at Trump's direction.

I think Cohen's cooperation with prosecutors is potentially more troubling for the president than Manafort's on-again, off-again dealings with Mueller, even though Manafort is the former campaign chairman.

With one exception, Manafort doesn't seem to know much about Trump and Russia (which is, you'll recall, the original reason for the investigation). The exception is the 2016 Trump Tower meeting with a Russian lawyer offering dirt on Hillary Clinton. But most of his legal liability has to do with dirty dealings with the likes of Ukraine. And now that we know Manafort was essentially acting as a double agent — having his lawyers brief the Trump team while supposedly cooperating with Mueller — his credibility is pretty much destroyed.

Cohen, too, is now an acknowledged liar, in both cases. But he said in the runup to his first plea that he had decided to break with his ex-boss and now tell the truth.

In yesterday's case, Mueller has emails showing that after the Trump Tower Moscow project supposedly died in January 2016, he continued his contacts with Russian officials and offered to fly to Moscow — with Trump's approval, Cohen says — to get the deal done. (Buzzfeed cited two law-enforcement sources as saying Cohen planned to offer Vladimir Putin a $50-million penthouse in the building to attract wealthy buyers.)

This may be just another rabbit hole since the trip never happened and nothing was ever built. Trump told reporters yesterday that as a businessman running for president he had every right to pursue new deals — especially since there was a "good chance" he wouldn't win — and he's right.

But this may be a piece of Mueller's puzzle. If he's trying to make the case that Trump was open to cooperating with Russia against Clinton's campaign, the prospect of a financial deal during the months when he was winning the GOP nomination could help his case. Or it could turn out to be nothing.

The president has been on a tear over the Mueller probe. He tweeted the other day:

"When will this illegal Joseph McCarthy style Witch Hunt, one that has shattered so many innocent lives, ever end-or will it just go on forever? After wasting more than $40,000,000 (is that possible?), it has proven only one thing-there was NO Collusion with Russia. So Ridiculous!"

One problem with this line of argument is that Cohen and Manafort, along with Michael Flynn, Rick Gates and others, can no longer claim to have been leading "innocent lives." They have all pleaded guilty to crimes.

But Trump did manage to make some other Russia news that has nothing to do with Mueller. After telling reporters that his meeting with Vladimir Putin at the G-20 was on, the president canceled it while flying to Argentina, as a protest against Russia seizing three Ukranian ships and their crew members. That, of course, counters the media narrative that he never stands up to Putin.