Watergate prosecutors had evidence that operatives for then-President Richard Nixon planned an assault on anti-war demonstrators in 1972, including potentially physically attacking Vietnam whistleblower Daniel Ellsberg, according to a never-before-published memo obtained by NBC News. 

The document, an 18-page 1973 investigative memorandum from the Watergate Special Prosecution Force, sheds new light on how prosecutors were investigating attempts at domestic political violence by Nixon aides, an extremely serious charge. 

NBC News is publishing the memo, and an accompanying memo about an interview prosecutors conducted with GOP operative Roger Stone, as part of special coverage for the 45th anniversary of the Watergate break-in.