ATLANTA — As Georgia secretary of state, Brian Kemp oversaw policies that critics say were intended to restrict voting by minorities and infrequent voters, including young people. Now, the Republican is the leader in a tight race for governor against Democrat Stacey Abrams, who is seeking to become the nation’s first black female governor. When Kemp oversaw voting, the state aggressively dropped inactive voters from the rolls, used an “exact match” policy that placed thousands of voter registrations on hold and investigated a voter registration drive by a group founded by Abrams. Kemp defends his tenure, saying his efforts were intended to improve election security. He also says increased voter registration and heavy turnout for last Tuesday’s election show the he was not trying to suppress the vote.