A court document filed by Special Counsel Robert Mueller’s prosecutors Tuesday night has an interesting footnote about Rick Gates, President Trump’s former deputy campaign manager and cooperating witness in Mueller’s investigation. Gates was “directly communicating in September and October 2016” with an unidentified person who “has ties to a Russian intelligence service and had such ties in 2016,” and Gates knew about this person’s ties to Russian intelligence, the filing says, calling the 2016 conversations “pertinent to the investigation.”