Donald Trump has his back to the wall. Seldom has so dismal a chapter been scripted in the constitutional history of the United States of America as it was on Tuesday.

As he lunges from crisis to crisis as President, his credentials have now plummeted to a level that may be difficult to burnish and not least with barely three months to go for midterm elections.

In two courts and in two cases brought by two different prosecutors, the US President’s former longtime lawyer, Michael Cohen, and his ex-campaign manager, Paul Manafort, were found to be guilty of bank fraud, tax evasion and paying off a porn star and a Playboy model in violation of federal campaign-finance law.

For special counsel Robert Mueller, it is a moment of spectacular triumph. Equally for President Trump, the loss of face has been direly shattering. Both Cohen and Manafort were convicted on eight counts. Manafort is scheduled to go on trial in Washington DC in September over his work in Ukraine.

Cohen has admitted in court under oath that he broke the law on the instructions of the US President. Mr Trump could do little but take to Twitter with advice to his followers not to hire Cohen. By any reckoning, the Trump presidency has entered a phase that is as critical as it is fraught.

Small wonder that he has been debunked by his detractors as a “mostly performative autocrat”. He has spoken in terms of locking up opponents but the net appears to be closing in on him.

Of course, he could theoretically exercise the presidential right to pardon those guilty. That constitutional option must be tempered with the possibility that any such move might in itself constitute grounds for impeachment. The case proceedings reflect poorly on the person helming the government of the world’s oldest democracy.

The midterm Congressional election in November could be a referendum of sorts on Trump’s presidency, however unofficial. For America as a nation, there is little to be enthused less than two years after Election 2016.

The Democrats stand a decent chance of retaking the House of Representatives, and perhaps even the Senate. Any miscalculation at this juncture by Trump could buttress the Democrat base. If the Democrats regain control of both Houses of Congress, they could re-hire Mueller as a “Congressional” special prosecutor should he be dismissed by the President.

It bears recall the Watergate investigation took two years to reach its logical conclusion. Chiefly, it brought down President Richard Nixon, reaffirming that the person helming the Oval Office is not above the law. Mueller needs to be shielded to prove that the system can work as well in 2018 as it did in 1972. After 46 years, the intrinsic values of democracy are on test in the US.