New York (CNN) The Donald Trump loyalist who famously said he'd take a bullet for the President is now willing to publicly fight his former boss.

Michael Cohen, the President's former lawyer, is prepared to campaign against Trump and Republicans in the midterm elections and the 2020 presidential race, a Democrat with knowledge told CNN. Marking the latest escalation in Cohen's growing animosity towards Trump, the source said he is open to doing a range of things to try to help the Democratic Party, including stumping for candidates, giving speeches and helping raise money.

Notably, Cohen, who according to his lawyer changed his party registration to Democrat last week, would call out and refute anything that he considers to be lies from Trump, this person said. (As of Tuesday morning, the New York State Board of Elections website still listed Cohen as a Republican.)

A political campaign against Trump would mark a new capstone in the already extraordinary public split between the two men. The rift has been on display for months, as Cohen has made it increasingly clear that he no longer had loyalties to his ex-boss.

Last month , ABC News reported that Cohen had sat for multiple interviews with investigators from special counsel Robert Mueller's office as well.

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