Politico is about to lose three of its most powerful and longtime leaders. Jim VandeHei, the co-founder and CEO of Politico; Mike Allen, author of the influential Politico Playbook; and Kim Kingsley, the company's chief operating officer will all leave the company later this year, sources with knowledge of the situation told CNNMoney on Thursday. Both VandeHei and Allen are expected to stay through the 2016 election. The exact date of Kingsley's departure is unknown. Politico is expected to release a memo regarding the news tonight, the sources said. VandeHei, Allen and Kingsley are three of Politico's most influential and...