Trump has taken to the internet to get his message out on the day of his arrest - "a tragic day for our Republic," as he put it.
An email went out to his mailing list with the subject "My last email before my arrest" in which he asks people to "chip in to save America", and includes a fundraising link. He also expresses concern that the US is becoming a "Marxist Third World country".
Soon after the email went out, Trump posted an all-caps message on Truth Social, the social media platform he owns, criticising the New York location of his court appearance later as a "very unfair venue with some areas that voted 1% Republican".
Trump also calls the judge who will arraign him "highly partisan" and says his family are "well-known Trump haters".
Trump says that Justice Juan Merchan, who oversaw last year's criminal trial of the Trump Organization, was "impossible to deal with during the witch hunt trial."