Federal prosecutors in New York are investigating President Trump’s longtime personal lawyer and fixer, Michael D. Cohen. : Faced with a sprawling investigation by the special counsel in Washington, President Trump must also contend with an independent-minded office of federal prosecutors in his hometown, New York, who are investigating his longtime personal lawyer and fixer, Michael D. Cohen. Mr. Trump’s administration had fired the Obama-era leader of the United States attorney’s office for the Southern District of New York last year, after initially asking him to stay on.