Georgia's Senate runoff between Warnock and Walker nears. What you need to know.

Early voting is fully underway in Georgia as voters head back to the polls to determine the last outstanding Senate race of the midterm elections: the runoff contest between Democratic incumbent Sen. Raphael Warnock and Republican challenger Herschel Walker.

While Democrats have been guaranteed control of the Senate, they have an opportunity to expand their majority after outperforming expectations in the Nov. 8 elections.

Both Warnock and Walker failed to earn more than 50% of the vote in Georgia's general election, triggering a runoff election Dec. 6 between only the two candidates.

Sen. Raphael Warnock, D-Ga., speaks during a news conference, Nov. 10, 2022, in Atlanta. Warnock is running against Republican Herschel Walker in a runoff election. Democrats have secured their majority in the Senate for the next two years. But holding on to Warnock's seat in Georgia's runoff next month could be crucial to their success.

What is a runoff?

Georgia has a unique election system in which a runoff election is held with only the top two vote-getters if no candidate earns more than 50% of the vote. The runoff election acts as a political tiebreaker, where a candidate has to earn a majority of the vote.

After the Nov. 8 elections, Warnock led Walker by more than 30,000 votes, but only earned 49.4% of the total votes – Walker earned 48.5%. Chase Oliver, the libertarian candidate, won 2.1% of the vote, which triggered the runoff.

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This will effectively be Warnock's fourth election in two years. He was previously elected to the Senate in 2020 in another runoff, but only for the remainder of the late Republican Sen. Johnny Isakson’s term, who retired due to health reasons.

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What’s happening?

In 2020, Georgia proved itself to be a battleground state, not to be taken for granted by either Democrats or Republicans. In his last runoff election, Warnock defeated incumbent Republican Sen. Kelly Loeffler by only 2 percentage points, at 51%to 49%. This runoff is looking to be just as close.

Republican Senate nominee Herschel Walker speaks to a crowd gathered for a rally with prominent Republicans on November 21, 2022 in Milton, Georgia.

Both parties are pulling out all the stops for the race. The campaign arm of Senate Democrats, the Democratic Senatorial Campaign Committee, announced a $7 million investment in field organizing efforts since the Nov. 8 election.

National Republicans have borrowed the popular political machine of Georgia's Republican Gov. Brian Kemp. The Senate Leadership Fund, a PAC with ties to Senate Minority Leader Mitch McConnell, R-Ky., is investing $2 million of its own money into the operation which includes voter outreach and data analytics.

High-profile campaign surrogates are getting in the mix as well. Former President Barack Obama will head to Georgia on Thursday to stump for Warnock. Obama was previously in Georgia in late October, and blasted Walker as “a celebrity that wants to be a politician.”

Former President Barack Obama greets Sen. Raphael Warnock, D-Ga., as he arrives at a campaign event for Georgia Democrats on October 28, 2022 in College Park, Georgia.

Kemp recently campaigned with Walker for the first time this fall. Walker lagged his Republican colleagues on the ballot on Nov. 8. Kemp won reelection with 2.1 million votes against Democrat Stacey Abrams, but Walker earned just over 1.9 million votes – about 200,000 fewer votes than Kemp.

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Kemp implored voters to not “believe the polls. Don’t believe the political pundits that are saying this race doesn’t matter anymore. It matters.”

What’s at stake?

Democrats won control of the Senate after flipping Pennsylvania’s Senate seat and defending key seats in Nevada and Arizona. But if Warnock wins, Democrats would expand their razor-thin advantage in the Senate to an outright 51-49 majority.

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In early 2021, Senate Majority Leader Chuck Schumer, D-N.Y., had to negotiate a power-sharing agreement with McConnell because the chamber was split evenly. Vice President Kamala Harris and her tie-breaking vote gave Democrats the majority.

A win in Georgia would also boost Democrats ahead of the 2024 elections, when 33 seats are up for reelection; Democrats will be defending 23 of them.

“It’s not about this December. It’s gonna be about November two years from now and the future of our country, y’all,” said Kemp, stumping for Walker.

Georgia Gov. Brian Kemp addresses his supporters at a watch party on election night on November 8, 2022 in Atlanta, Georgia. Kemp defeated Democratic challenger Stacey Abrams in a repeat of their 2018 race.

This article originally appeared on USA TODAY: Georgia's crucial Senate runoff between Warnock and Walker nears