Donald Trump may not have been on the ballot, but that hardly stopped American voters from delivering a stinging rebuke on his presidency.

And as the Republican rout became increasingly apparent, the president, never one to let reality have the last word, took to social media to offer his own post-mortem.

"I wasn't on the ballot and if I was, we would have won in a landslide!" he declared, before signing off with his trademark flourish: "Thank you for your attention to this matter."

He later posted on social media platform Truth Social a photo of a baseball hat with the word “Veto” emblazoned across the front.