ATLANTA — Nathan Deal is narrowly leading Jason Carter in the general election for governor, according to a poll released Tuesday by a Florida university. The results of the St. Leo University survey also shows Deal, the Republican governor, is better known and better liked six months before the general election and ahead of any ads about his opponent. In the matchup between Deal and Carter, the Democratic nominee-apparent, the incumbent had the support of 38 percent to Carter’s 35 percent.