Almost daily, Donald Trump breaks the mould of how a president should behave.

But Tuesday in Washington showed he still has the power to shock.

For the third day in a row, the President ramped up a series of public attacks on one of his most loyal supporters, Attorney-General Jeff Sessions.

In Mr Trump's latest tirade on Tuesday, he called Sessions "very weak" for not launching a prosecution against former Democratic rival Hillary Clinton over her use of a private email server — during the election campaign, Mr Trump often led his crowds in chants of "lock her up".

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But Mr Trump has been angry at Mr Sessions since March.

Back then, Mr Sessions had just been confirmed as Attorney-General.

But he was already under fire, after it was revealed he had two meetings with the Russian Ambassador to the US while working with the Trump campaign — meetings he neglected to mention during his Senate confirmation hearing.

Mr Sessions took the advice of his Justice Department, and recused himself from involvement in any investigations into Russian influence on the campaign.

As a result, Mr Sessions was not involved in the decision by the Deputy Attorney-General to appoint Special Counsel Robert Mueller to investigate Russian interference in the election.

Mr Trump has called that investigation a "witch hunt" — as it broadens to include his tax returns and business dealings.

Jeff Sessions has been one of the President's most loyal supports. ( Reuters: Aaron P Bernstein )

The President told the New York Times he felt Mr Sessions' recusal was "very unfair to the President", and that if he had known the Attorney-General was going to recuse himself, he would never have given him the job.

On Monday, he vented at Republicans in general on Twitter for not protecting the President.

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Now, he is trying to force his Attorney-General to resign. But Mr Sessions is not going.

The concern is that if Mr Trump fires Mr Sessions, it will be seen as preparing the ground to find a new Attorney-General who will do the unthinkable for the President — fire Mr Mueller.

That possibility is being discussed in Washington in terms like 'constitutional crisis'.

There is so much going on in Washington at the moment, it's hard to know where to look.

Spotting a strategy in the President's actions is equally difficult.

All this is happening at a time when Mr Trump is relying on Republican senators to get a deeply unpopular healthcare bill through Congress.

Turning on Jeff Sessions — one of Mr Trump's earliest and most loyal supporters — is hardly a way of inspiring them to take a political risk for their President.

Especially when he's also proven so willing to shift the blame.