GOP presidential candidate Herman Cain’s longest serving aide is leaving his surging campaign, even as the former Godfather’s Pizza CEO polls in the top tier of the Republican field, The Daily Caller has learned. Executive assistant Karleen Smith has worked for Cain since he ran for the U.S. Senate in 2004. In an email to TheDC, she said her departure from the Cain campaign has long been in the works. “My husband retired in July and I am 59,” Smith said. “My husband and I have been planning this retirement for awhile. We are ‘young seniors’ and ready to travel...