David P. White will be stepping down later this spring from his role as National Executive Director and Chief Negotiator for the entertainment media industry’s largest union after a 12 year run, SAG-AFTRA announced on Friday.“David has been an invaluable advocate for our members and deserves immense credit for SAG-AFTRA’s success over the past decade,” SAG-AFTRA President Gabrielle Carteris said in a statement.