Cohen's defense attorney, Lanny Davis, announced on Twitter that his client has changed his registration from Republican to Democrat. He described the move as an effort to distance "himself from the values of the current" administration.
Cohen retweeted Davis' post and a link to an Axios story that first reported the news.
The switch came on the eve of Friday's deadline for New Yorkers to register to vote in the November election.
Cohen had been a registered Democrat for years until changing his registration in March 2017. "It took a great man to get me to the make the switch," Cohen said at the time on Twitter, referring to Trump.
Cohen had served as the Republican Party's deputy finance chairman but resigned that post this year amid a criminal investigation into his business dealings.
Davis on Thursday described Cohen's latest about-face as "another step" in Cohen's promise to place "family and country first," a pledge he made over the summer that signaled his willingness to cooperate with special counsel Robert Mueller's investigation of Russian interference in the 2016 election.
Cohen pleaded guilty in August to eight federal charges, including tax evasion, bank fraud and campaign finance violations. In pleading guilty, he said that Trump directed him to arrange payments before the 2016 election to buy the silence of porn actress Stormy Daniels and a former Playboy model who alleged they had affairs with Trump.
Cohen is scheduled to be sentenced Dec. 12.
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