Ex-mayor Richard Riordan, who backed Bob Hertzberg in this year's primary, is returning today to the Villaraigosa fold, the Daily News' Rick Orlov reports. Riordan had endorsed Villaraigosa in the 2001 runoff too, and this really isn't a surprise since it was apparently well known that as mayor Riordan had a low opinion of then-City Attorney Hahn. The endorsements are coming faster now, though Hertzberg and Bernard Parks are still hold outs. Villaraigosa also picked up another former Hahn backer in Rep. Jane Harman—at a press conference slamming Hahn's LAX plan—and the San Fernando Valley Young Democrats, who were with Hertzberg in the primary. Since we last checked in, Hahn has picked up termed-out ex-councilman Nate Holden, a former aide to Hahn's father who says "you don't trade in proven old friends for unproven new ones."