It came as Trump claimed to have raised $39 million, largely from small-dollar donors, since his conviction. 

He argued that the vast sum had been matched by a bump in the polls, which previously had him level pegging with Mr Biden, and was proof Americans saw that his guilty verdict went “far beyond me”.

“This is bigger than Trump. This is bigger than me, this is bigger than my presidency,” he said.

Senior Republicans in Congress have rallied behind their presidential candidate, including Mitch McConnell, the GOP Senate leader, who has endured a frosty relationship with Trump.

Mr McConnell said the charges against Trump “never should have been brought” and he expected them to be “overturned on appeal”.

Mr Johnson also repeated his endorsement of Mr Trump in the 2024 race, saying: “Whatever his detractors may say, I believe that Donald Trump – at his best – could offer the world the strong, confident leadership that it needs.”