FILE PHOTO: Singer Bret Michaels performs on "Fox & Friends All-American Summer Concert" series in New York July 18, 2014. REUTERS/Lucas Jackson/File Photo LOS ANGELES - Bret Michaels, frontman of Poison, the rock group best known for its working-class anthem "Nothin' But a Good Time," has withdrawn from a concert series commemorating the United States' 250th anniversary, the latest in a wave of cancellations.