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Donald Trump’s weekend of assaults on Robert Mueller’s investigation pushed Washington closer than ever to the major crisis of governance that could ensue if the President were to act on his fury and fire the special counsel.

The President’s lambasting of the Russia probe and the administration’s sacking of former FBI deputy director Andrew McCabe prompted warnings from key Republicans that he would send the country over a cliff if he tried to dismiss Mueller.

And the White House will Monday face uncomfortable new questions about the Trump team’s conduct during the 2016 election after Facebook suspended Cambridge Analytica, a data firm used by President’s campaign, over allegations it used the data of 50 million users of the social media site without their permission.

Trump’s major agenda push this week will highlight his plan to tackle the opioid crisis. But it’s a good bet that initiative will be overtaken by a fresh round of West Wing chaos, speculation about personnel shake-ups and revelations about the legal duel between the President and Stormy Daniels, a porn star who claims she had an affair with Trump more than decade ago.

But, far from being put off by the turmoil rocking his administration, Trump appears to be relishing a new chapter of his presidency, as he axes and undermines aides he distrusts and gives his impulsive personality free rein.

The result is that the President is leading Washington, the nation and the world into an even more unpredictable phase, testing the limits of his political power at home and putting the international system under extreme strain.

CNN Money: Facebook investigating employee’s links to Cambridge Analytica

Trump spent the weekend gloating over the firing of McCabe, who he portrayed as the epitome of corruption at the tip of the bureau, and one of those responsible for what he sees as the unjustified investigation into allegations of collusion between his campaign and Russia.

But sources familiar with the matter told CNN’s Kaitlan Collins that as he phoned his outside advisers and allies over the weekend, Trump’s growing irritation with special counsel Robert Mueller overshadowed his delight over McCabe’s late-night dismissal. He escalated his assault on Mueller over the weekend in a way that made it look like an attempt to fire the special counsel, once thought impossible owing to its constitutional implications, is very much on his mind.

“The Mueller probe should never have been started in that there was no collusion and there was no crime,” Trump wrote on Twitter Saturday night. He reiterated that point Monday morning, dismissing the investigation as a “WITCH HUNT.”

McCabe was fired at the recommendation of an FBI internal disciplinary process into his handling of the Hillary Clinton email investigation. But suspicions he was cast out for political reasons have been stoked by Trump’s incessant public campaign for his ouster.

McCabe, however, hit back at his firing and complained that he had been pushed out hours before he was due to retire because Trump wanted to slander the FBI and the Mueller probe, in which he is a key witness.

Trump’s fresh attacks on Mueller immediately renewed speculation that the President would try to dismiss the special counsel, potentially by replacing Attorney General Jeff Sessions, who is recused from any matter relating to the 2016 elections, and replacing him with an ally willing to do his bidding.

That prospect prompted some Republicans to warn that Trump was on the threshold of dangerous territory.

“I think that people see that as a massive red line that can’t be crossed,” Arizona Sen. Jeff Flake said on CNN’s “State of the Union.”

“So, I hope that that’s the case. And I would just hope that enough people would prevail on the president ‘now, don’t go there. Don’t go there.’”

South Carolina Republican Sen. Lindsey Graham warned that if Trump fired Mueller he would face grave consequences.

“As I have said before, if he tried to do that, that would be the beginning of the end of his presidency, because we’re a rule of law nation,” Graham said.

Trump’s lawyer Ty Cobb however told CNN’s Gloria Borger on Sunday night that nothing had changed in the White House’s attitude to the special counsel.

“In response to media speculation and related questions being posed to the administration, the White House yet again confirms that the President is not considering or discussing the firing of the Special Counsel, Robert Mueller,” Cobb said.

One reason why Trump may be lashing out at Mueller is the special counsel seems to be edging closer to the President by the day. Last week, it emerged that he had subpoenaed documents from the Trump organization – including some that related to its business dealings with Russia.

But the Russia probe is not the only source of turmoil rocking Washington.

Who is next for the chop?

Many White House and Cabinet officials return on Monday with the axe hanging over them, after Trump said last week following the firing of Secretary of State Rex Tillerson that he was finally gathering the team he wanted around him.

Among those thought to be on the way out or on borrowed time include national security adviser H.R. McMaster, White House chief of staff John Kelly, and cabinet members including Housing and Urban Development Secretary Ben Carson and Veterans Affairs Secretary David Shulkin, who are like many colleagues fighting off scandals related to lavish spending.

The extraordinary legal showdown between the President and Stormy Daniels, who said she had an affair with Trump long before he ran for office is certain to escalate in the days ahead – if for no other reason than the porn star’s lawyer is determined to keep her case in the news.

On Friday, attorneys defending Trump and the company of his personal legal counsel, Michael Cohen, filed to move the lawsuit to federal court and claimed she could owe in excess of $20 million for violating a nondisclosure agreement.

The world outside the United States, reeling after several weeks of mind-boggling Trump behavior that matched the disruption his supporters had in mind when they elected him, will keep a close eye on Washington this week.

There remains no clarity on the administration’s strategy heading into the President’s planned summit with North Korean leader Kim Jong Un which the White House has said will take place as soon as May.

The fate of the Iran deal, that Trump is threatening to scrap by May but is strongly backed by America’s European allies, will be in focus when the President welcomes Saudi Crown Prince Mohammed bin Salman to the White House on Tuesday.

And the reverberations from Trump’s demand for import tariffs on aluminum and steel are still powering a frantic effort by US allies to win opt-outs.

A White House plan to crank up the heat on China’s trade practices that is in preparation behind the scenes could drive a new nail into the coffin of the World Trade Organization and spark global economic turmoil.