Brushing aside last week's controversy over Trump's sacking of FBI director James Comey, Dershowitz - one of the country's preeminent constitutional authorities - didn't mince his words on the latest controversy.

"Let's not minimise it [by comparison]," he said. "Comey is in the wastebasket of history. Everything else is off the table ??? Let's not underestimate it."

A week ago, Trump was dismissing "this Russia thing" as fake news, a witch-hunt.

Yet there he was, just 24 hours after sacking the man in charge of the investigation of his campaign's complicity in Russia's meddling in the 2016 election campaign, sharing closely-held US intelligence secrets as he chewed the fat with Russian Foreign Minister Sergei Lavrov and Moscow's ambassador to the US, Sergey Kislyak, a key figure in the Russia scandal, at a cosy White House meeting.

As is his wont, Trump boasted to Lavrov about all the things he knows - telling him: "I get great intel. I have people brief me on great intel every day," an official familiar with the exchange told The Washington Post, which broke the story.

By all accounts, the President did not disclose the methods by which the information had been garnered. But in outlining proposed Islamic State (IS) plots and the damage they could inflict, he named the city in IS territory where the US intelligence partner detected the threat.

The Post withheld the name of the city lest it contribute to exposing the foreign source whose intelligence had been shared with Washington. But a source described as "a former senior US counter-terrorism official who also worked closely with members of the Trump national security team" told the paper: "Everyone knows this stream is very sensitive, and the idea of sharing it at this level of granularity with the Russians is troubling."

The problem here, as seen by counter-intelligence experts, is that Moscow, informed of the city in which the intelligence had been gathered, could identify the US ally or intelligence operatives involved - whose government had not authorised a sharing of the information.

A former intelligence official and expert on Russia surmised that on the basis of the clues provided by Trump: "I don't think that it would be that hard [for Russian spy services] to figure this out."

A current official told the Post: "If that [intelligence sharing] partner learned we'd given this to Russia without their knowledge or asking first, that is a blow to that relationship."

If Trump was not aware of his gross indiscretion, others around him were - aides reportedly made damage-control calls to the CIA and ordered that the offending exchange be stricken from records of the meeting, lest it leak to the media.

After the fumbled Comey sacking, it came as no surprise that the White House conspicuously tried to have all voices singing from the same hymnsheet as it attempted to drown out the Post's report. The only trouble was they set up an irrelevant strawman to knock down.

Despite the Post's careful reporting that Trump had not disclosed intelligence-gathering methods, that turned out to be the cornerstone of statements by National Security Adviser H.R. McMaster and Secretary of State Rex Tillerson.

This from McMaster: "There's nothing that the President takes more seriously than the security of the American people. The story that came out tonight, as reported, is false. The President and the foreign minister [Lavrov] reviewed a range of common threats to our two countries, including threats to civil aviation.

"At no time - at no time - were intelligence sources or methods discussed. And the President did not disclose any military operations that were not already publicly known. Two other senior officials who were present, including the Secretary of State, remember it being the same way and have said so. Their on-the-record accounts should outweigh those of anonymous sources. And I was in the room. It didn't happen."

Yet if there was any uncertainty about weekend reports of Republican senators backing away from Trump, Bob Corker of Tennessee made the mood in the party plain: "Obviously, they are in a downward spiral right now and have got to figure out a way to come to grips with all that's happening. And the shame of it is, there's a really good national security team in place.

"The chaos that is being created by the lack of discipline is creating ... a worrisome environment."

The trouble for Republicans is that such is the topsy-turvy nature of this administration's damage control that they no longer know what to believe - too many have been caught out defending Trump on the basis of Script A, only to wake up the next morning to find that the administration has shifted to the opposite argument in Script B.

It all makes the GOP and Trump-stoked drama about Hillary Clinton's dodgy email server seem a bit, well, dodgy.

Their mantra through last year's election campaign was that because of the threat of hacking, any classified information that passed through the Clinton server could end up in the hands of others - but here we have Trump serving up secrets on a silver platter.

Remember Trump surrogate Michael Flynn, who served briefly as national security adviser before Trump sacked him for lying about his communications with Moscow, only after the lying was exposed in the media?

Here's Flynn before he joined the "lock her up!" chorus at a Trump rally: "I have called on Hillary Clinton to drop out of the race because she, she put our nation's security at extremely high risk with her careless use of a private email server."

And here's a great Trump tweet from July last year, in which he relies on Comey's criticism of Clinton: "Crooked Hillary Clinton and her team 'were extremely careless in their handling of very sensitive, highly classified information'. Not fit!"

And at a Florida rally in the same month: "So how can Hillary Clinton be briefed on this unbelievably delicate information when it was just proven that she lied and that her server shouldn't have had it and that they're missing 33,000 emails and that's just the beginning ??? I don't think that it's safe to have Hillary Clinton, in light of what just happened, and in light of what we just found out, I don't think it's safe to have Hillary Clinton be briefed on national security because the word will get out."

It came as no surprise at all that, when polled last week by Quinnipiac University for the first word that comes to mind when they think of Trump, nearly twice as many as those who offered "President" offered "idiot".