ATLANTA (AP) — Voters have begun casting their ballots in Georgia's competitive races for U.S. Senate and governor.

But it's still unclear how many people are eligible to vote in this fall's general election. A lawsuit filed Friday asks a judge to force Secretary of State Brian Kemp and election officials in five counties to promptly review voter registrations before Election Day on Nov. 4.

The suit says more than 40,000 people who participated in a registration drive are missing from state voter rolls.

Early voting began Monday in several counties.

Democrats hope the state's changing demographics and efforts to register new voters will boost their candidates in the tight races for U.S. Senate between Michelle Nunn and Republican David Perdue, and the governor's race between Jason Carter and Republican incumbent Nathan Deal.