Michael Cohen, the former personal lawyer to President Donald Trump, leaves federal court after reaching a plea agreement in New York. File picture: Craig Ruttle/AP

Washington - US President Donald Trump's former long-time personal lawyer Michael Cohen on Friday said US voters should cast their ballots against the Republican Party on November 6 or else they will face more "craziness."

Cohen, who last week changed his party affiliation from Republican to Democrat, said on Friday he's been a Democrat "pretty much [his] whole entire life."

Cohen's lawyer Lanny Davis tweeted Cohen's party switch last week, adding that Cohen was "distancing himself from the values of the current" administration.

In a tweet on Sunday, Cohen said the upcoming midterm elections might be "the most important vote" of people's lives and urged them to vote.

Asked about that message by a CNN reporter on Friday, Cohen went further. "Listen, here's my recommendation: grab your family, grab your friends, grab your neighbours, get to the poll because if not you are going to have another two or another six years of this craziness. Make sure you vote."

Cohen switched to the Republican Party last year only because of a request from top party officials so that he could take a leadership role in the party.

Cohen, who once said he would "take a bullet" for Trump, is scheduled to be sentenced in December for facilitating non-disclosure agreements and payments ahead of the 2016 election to porn star Stormy Daniels and Playboy model Karen McDougal, who say they had affairs with Trump in 2006.

Cohen pleaded guilty in August to committing campaign finance violations in relation to the payments, which exceeded federal limits for campaign donations.