Miami Mayor Manny Diaz's time as head of the U.S. Conference of Mayors has come to an end, and usually the sitting American president sends administration officials to the conference -- this year held in Providence, Rhode Island -- but the Obama administration pulled out. The reason: Providence Mayor David Cicilline is in a labor dispute with the firefighters' union, and the group was picketing the event. Vice President Joe Biden was scheduled to attend, but the White House said it would not br
