Special counsel Robert Mueller is closing in on President Trump, according to a journalist who helped expose wrongdoing by former President Richard Nixon that helped lead to the only White House resignation in history.

CNN’s Carl Bernstein, who with Washington Post colleague Bob Woodward in the early 1970s broke a series of key stories on Watergate, on Sunday cited a recent sentencing memo regarding Michael Cohen, Trump’s former fixer. That could prompt impeachment proceedings against the president, Bernstein said. Federal prosecutors in New York filed the document last week.