The husband of White House adviser Kellyanne Conway has donated the maximum amount permitted for an individual to Joe Biden’s presidential campaign — and mocked Donald Trump with the receipt.

George Conway, a devoted critic of Mr Trump’s, donated $2,800 to Mr Biden on Super Tuesday as the former vice president stormed to victory in at least nine states.

Explaining his decision to donate, he told New York magazine reporter Olivia Nuzzi: “The nation can’t afford four more years with a megalomaniacal moron in the White House.” Mr Conway has now made the receipt for the donation his Twitter banner image.

He has made a campaign of sorts out of railing against Mr Trump, criticising him as a threat to the future of the republic and a chief executive unfit for office.

In a piece for the Atlantic last October, Mr Conway wrote: “You don’t need to be a mental-health professional to see that something’s very seriously off with Trump.

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“No president in recent memory — and likely no president ever — has prompted more discussion about his mental stability and connection with reality.”

As Super Tuesday’s results came in, Mr Trump tweeted a stream of seemingly disconnected musings and claims, and Mr Conway responded hawkishly to each one.

“This is a man who put fidelity to the law over personal loyalty,” he wrote, “and the fact that you can’t comprehend that is one of countless illustrations why you’re entirely unfit for public office, @realDonaldTrump.”

Mr Conway also suggested that Democratic candidate Michael Bloomberg, who has ploughed more than $500m of his own money into his campaign to little avail, should set up a Super PAC to plough money into the the election.