WASHINGTON 

Polls across the US state of Georgia began closing Tuesday night in what is promising to be a nail-biting runoff contest to determine whether Sen. Raphael Warnock will defend his seat or if it will be claimed by Republican challenger Herschel Walker. 

Polls began closing at 7 p.m. local time (0000GMT) across the state, though many remained open to allow people who got in line before then to cast their ballots. Many Georgians throughout the day braved frigid temperatures and rain to take part in the contest.

Walker, a former American football star, and Warnock are in the runoff election after neither candidate secured the 50% needed to win November's midterm election. Last month’s race saw Warnock hold a razor-thin 0.9% edge against Walker with libertarian candidate Chase Oliver claiming a little more than 2% of the vote. Oliver was eliminated following the results.

Walker, who is backed by former US President Donald Trump, a figure he emulates, has been dogged by claims that he paid for two former girlfriends to receive abortions despite touting himself as a staunchly anti-abortion candidate. Walker has denied the charges.

The results of the contest will determine whether Democrats hold a 51-seat majority in the 100-member chamber or if the Senate continues to be split 50-50 along party lines as it has been for the past two years.

In either event, Democrats will control the Senate because of a longstanding tradition that gives control of the chamber to the president's party when it is evenly split. Vice President Kamala Harris wields a tie-breaking vote as president of the Senate.

Republicans have failed so far to flip any Senate seats in this year's midterm elections.

Media outlets could announce a winner within hours of polls closing.