“I hereby demand, and will do so officially tomorrow, that the Department of Justice look into whether or not the FBI/DOJ infiltrated or surveilled the Trump Campaign for Political Purposes – and if any such demands or requests were made by people within the Obama Administration!” Trump wrote.

Shortly after his outburst, the Justice Department said its inspector general had been asked to assess whether there was any political impropriety in the use of the confidential source, as part of an existing probe into aspects of the Russia investigation.

Deputy Attorney General Rod Rosenstein, who is overseeing Mueller’s activities, said in a statement, “If anyone did infiltrate or surveil participants in a presidential campaign for inappropriate purposes, we need to know about it and take appropriate action.”

It was possible that Rosenstein punted the matter to the inspector general to avoid a direct face-off between the White House and the Justice Department.

But his move poses a fateful question that could be answered as soon as Monday: will the President flex his muscle further to demand the Justice Department turn over documents on the source to his allies on Capitol Hill? That action could potentially force senior officials in the department to consider whether to remain in their positions.

Were Rosenstein to resign under pressure for instance, it could help Trump if he is able to eventually install an official that might be hostile to the Mueller investigation.

There appears to be nothing illegal in Trump’s demand for a Justice Department investigation — just as in practice, he had the authority to fire FBI Director James Comey last year.

But some critics believe that Trump’s repeated pattern of leaning on the Justice Department and the FBI over the Russia investigation could come close to showing intent that could amount to obstruction of justice.

Even the fact that Rosenstein asked the inspector general — the internal Justice Department watchdog — to get involved, puzzled some analysts.

CNN legal analyst Paul Callan said that he found it “bizarre” that Rosenstein acted on an order to start an investigation via tweet.

“I mean, wouldn’t the President call him in? Wouldn’t there be a little bit of nuance in the order?” Callan asked, speaking with CNN’s Ana Cabrera.

Trump’s intervention appeared to go beyond his already intense anger about the Mueller probe, his hypersensitivity to suggestions his election win was not legitimate, and the efforts to tarnish Mueller.

If the allegations were true, they would potentially mean that someone in the Obama administration had ordered the FBI to spy on the Republican nominee for political reasons and the bureau had agreed to do it.

On Monday morning, in a furious volley of tweets, Trump highlighted a Wall Street Journal opinion piece from last week that asked what former President Barack Obama knew about “how the government came to investigate the presidential campaign of the party out of power.”

“The Wall Street Journal asks, ‘WHERE IN THE WORLD WAS BARACK OBAMA?’ A very good question!” Trump tweeted.

Certainly, it would be a stunning political crime if it was proven the former administration was acting out of political motivations. But given that no one has offered any evidence for such an outlandish scenario, it seems not to be rooted in fact at this point.

CNN has reported that the confidential source was not someone planted by the FBI inside the campaign, at a time when the bureau was investigating alleged Russian election interference.

The New York Times, citing individuals familiar with the matter, reported Friday that the confidential source interacted with Trump campaign advisers George Papadopoulos and Carter Page.

The Washington Post reported that in addition to Page and Papadopoulos, the source met with Sam Clovis, the Trump campaign’s co-chairman, to talk about relations with China. Clovis’ attorney told the Post that Russia never came up in their conversation.

Former CIA operations officer Robert Baer said there was nothing unusual about the FBI using a confidential source in what was a counter-espionage investigation spurred by fears Russian intelligence was trying to infiltrate the Trump campaign.

“That is what the FBI does for a living. It stops espionage. To do that, they run confidential informants into the suspects,” said Baer, a CNN national security analyst.

White House spokeswoman Sarah Sanders said Sunday she had nothing to add to the President’s tweets.

But former Trump adviser Steve Cortes told CNN that Papadopoulos was a “deeply irrelevant figure” in the campaign.

“There was no collusion. And by the way, even if there was collusion, which there wasn’t, not a crime. So what we have here is an investigation in search of a crime, which is utterly un-American,” said Cortes. “What I think the President is finally doing, thank goodness, is saying ‘enough of this nonsense.'”

Ali Soufan, a former FBI special agent who played a key role in combating Al-Qaeda before and after the September 11, 2001, praised Rosenstein’s move.

“Smart response by DOJ! They potentially voided a constitutional crisis by politely, yet effectively, sidelined the President’s attempt to interfere in an ongoing investigation. The Mueller probe continues…for now,” said Soufan.

Sunday’s developments in Trump’s campaign against the Russia probe come at a moment when his defense seems to be evolving. Increasingly, his supporters appear to be implicitly raising the possibility that his campaign team was lured into any wrongdoing by an FBI ruse.

On Friday, Trump quoted Fox Business Network anchor David Asman in a tweet.

“Apparently the DOJ put a Spy in the Trump Campaign. This has never been done before and by any means necessary, they are out to frame Donald Trump for crimes he didn’t commit,” Trump wrote, citing Asman.

Another new theme of Trump’s top legal adviser Rudolph Giuliani is that if anyone in the Trump campaign did work with Russia to use dirt against Democratic nominee Hillary Clinton, they would not have been doing anything wrong.

“There is nothing illegal about that. Even if it comes from a Russian or a German or American, it doesn’t matter,” Giuliani said Wednesday on the “Ingraham Angle” on Fox News.

On the face of it, it doesn’t seem that such justifications would be chosen by someone who believed they were about to be cleared by the Mueller investigation.

Yet such is Trump’s fury over the whole affair, it’s also conceivable that his volcanic temperament and belief that he is being unfairly targeted is causing him to act in a way that raises suspicions.