By Brad Heath

WASHINGTON (Reuters) – Nearly 2.1 million people have cast ballots in a U.S. Senate runoff election in Georgia that will determine whether Democrats control both chambers of Congress, according to state data published Thursday.

More than a quarter of the state’s registered voters have either cast ballots early or through the mail, the state’s figures show, a sign that turnout in the pair of Senate races will be high. About 4 million Georgians voted early in the November election.

The runoffs pit Democratic challengers Raphael Warnock and Jon Ossoff against Republican incumbents Kelly Loeffler and David Perdue, respectively. The runoff election was necessary because no candidate won more than 50% of the vote on Nov. 3.

The state releases information about the number of people who voted, but does not tally their votes until election day.

About 1.3 million people voted early at in-person polling places, according to the state data. Another 721,000 sent ballots by mail. A total of about 1.3 million Georgians requested mail-in ballots.

Voting in the Senate runoffs ends on Jan. 5.

Turnout has been higher in some of the heavily populated areas around. About 30% of registered voters in Fulton County, which includes Atlanta, had voted by Thursday, as had about 32% of voters in suburban DeKalb County.

(Reporting by Brad Heath; Editing by Noeleen Walder and Alistair Bell)