 In 2005 and 2006, U.S. intelligence warned McCain's Senate staff about the Senator's involvement with Davis, who was then a lobbyist in business with Paul Manafort, but U.S. intelligence gave no further warnings about Davis's Russian connections when Davis was McCain's national campaign manager from July 2007 to November 2008.Other top staffers included McCain's former chief of staff Mark Salter and long-time political strategist Charlie Black who worked for Reagan, both Bushes and South Carolina Senator Lindsey Graham.Former Bush advisor Mark McKinnon also worked for the campaign before leaving in May 2008 to avoid working against Barack Obama.