In the latest of his mounting legal problems, Fulton County District Attorney Fani Willis has charged Trump on 13 counts related to his alleged effort to overturn the 2020 election results in Georgia. In total, the ex-president now faces 91 charges in the four criminal cases.

Trump has denied any wrongdoing and claimed repeatedly that he is the victim of a biased political vendetta. “What has taken place here is a travesty of justice,” he said on the tarmac after being arrested and booked. “We did nothing wrong.”

At the jail, Trump was listed as inmate P01135809 weighing 215lbs (98kg), with his hair colour listed as “blond or strawberry”, his image immortalised in a scowling mugshot that some commentators speculated was rehearsed.

Unlike the other cases, he will not be formally arraigned – an initial hearing when charges are read out and the defendant pleads guilty or not guilty – until next month.

On Thursday, Republican lawmakers in the US House of Representatives launched an investigation into Willis, spearheaded by House Judiciary Committee chairman Jim Jordan, who is among Trump’s staunchest allies in Congress.

In a letter to Willis, the Ohio Republican pointedly asked whether she coordinated the Georgia investigation with the US Justice Department or used federal tax money to carry out her probe.

“The federal government has a substantial interest in the welfare of former presidents,” Jordan said in his five-page letter.

Despite years of flagrantly defying political norms – he recently referred to fellow Republican contender and former New Jersey governor Chris Christie as a “fat pig” and has publicly embraced his many indictments – he continues to enjoy over 50 per cent approval ratings among Republicans, three times that of his nearest rival, Florida Governor Ron DeSantis.

Legal experts have said the fundamental pillar of his defence strategy is delay, which would allow him, he hopes, to retake the White House, pardon himself and stay out of jail. Some have suggested that his motivation in running for president is as much about avoiding conviction as it is to run the country.

But presidents do not have the authority to grant clemency in state cases. Willis is also expected to present particularly dramatic evidence that jurors can easily understand, including a recording of Trump telling Georgia Secretary of State Brad Raffensperger: “I just want to find 11,780 votes” – the margin he trailed now-President Biden in the crucial swing state.

But the case is not without risk for the prosecution. Willis has employed a novel legal strategy, charging Trump and 18 co-defendants with racketeering, a count often associated with organised crime prosecutions, in addition to other charges, alleging a conspiracy to defraud Georgia voters. The sprawling case also could take years before it is resolved.

His history of outrageous and inflammatory attacks in public could be challenged in court, however. Under his bail terms, he is not allowed to intimidate witnesses or other defendants or “obstruct the administration of justice,” a trenchant warning given past behaviour.

Despite his defiance, however, there are signs of strain. He has shaken up his various legal teams repeatedly. He will have to juggle court and campaign appearances. And up to 75 per cent of his large political war chest has been spent on paying law firms.

Additional reporting by agencies