A former New York gubernatorial candidate who once operated a high-end escort service, Kristin M. Davis, testified over the summer to a grand jury in the special counsel’s Russia investigation that she overheard left-wing comedian Randy Credico admit that he was a back channel between Trump confidant Roger Stone and WikiLeaks. Davis, a longtime friend of Stone’s, told The Daily Caller News Foundation that she testified on Aug. 10 that she “heard the tail end of a conversation where Credico was trying to impress upon Roger not to disclose his name.” That makes her the third grand jury witness who...