Bart Haggerty, a longtime critic of the borough's party bosses, starts as deputy clerk of the Board of Elections Queens office late this month. He replaces Gisela Mengler, who is retiring from the agency. Haggerty, a political operative who has worked as chief of staff to City Councilman Eric Ulrich -- the borough's only Republican elected official at present -- has served the Board as a trainer in the past. He also worked on former Mayor Michael Bloomberg's 2005 re-election campaign. Haggerty, who has had a long career in directing, teaching, and performing music in a pastoral setting, is the scion of a Queens political family. His father, John Haggerty Sr., was a well-known figure in New York politics. His brother, operative John Haggerty Jr., was convicted of swindling Bloomberg of $750,000 that was supposed to go for a poll-watching operation in the 2009 election.