Robert Mueller’s investigation is vital to ensure that the American republic survives the threat posed by having lawbreakers close to the centre of US power

There has never been an hour in the history of the American republic like it. On Tuesday, separated by 230 miles and 60 minutes, in two courts, in two cases brought by two different prosecutors, a US president’s former longtime lawyer, Michael Cohen, and his ex-campaign manager, Paul Manafort, were found to be crooks: guilty of bank fraud, tax evasion and paying off a porn star and a Playboy model in violation of federal campaign-finance law. Then again, there has never been a president like Donald Trump.
Mr Trump is a self-aggrandising liar whose desire for riches, infamy and adoration appears insatiable. The father of the US constitution, James Madison, once said that if men were angels they would not need government. But what if government itself is possessed by a character like Mr Trump? That is the threat the work of the special counsel Robert Mueller has been uncovering.
Mr Mueller had his best day on Tuesday. Both Cohen and Manafort had been in Mr Mueller’s sights. Both were convicted on eight counts, although Mr Mueller had handed over Cohen to the New York attorney’s office to prosecute. It is not the end of the story for Manafort, who is scheduled to go on trial in Washington DC in September over his work in Ukraine. Neither has Cohen finished. In court he admitted under oath that he broke the law at the direction of the president. Cohen has a reason to cooperate with Mr Mueller – he can reduce his sentence if he assists in further investigations. No wonder Mr Trump took to Twitter recommending that his followers not hire Cohen.
We are now entering a critical and dangerous period of the Trump presidency. Until now Mr Trump has been a mostly performative autocrat. He has encouraged the idea that he will lock up opponents, but he has not done so. Mr Trump attacks the “fake news” media but he has not sent thugs to smash printing presses. Yet the net is closing in on Mr Trump and his family. Mr Trump could spike Mr Mueller’s guns by pardoning all those found guilty – though that move might itself constitute grounds for impeachment.
  How to impeach a US president – video