(AP) – Two years ago, control of the U.S. Senate came down to Georgia, with two pivotal runoff election wins tipping the chamber’s favor into Democratic hands.

This fall, it’s possible the newly minted battleground state could again play a major role in how the Senate shakes out, with a marquee contest that, thanks to a third-party candidate, may not be decided until a runoff election a month after Nov. 8.

Here’s a look at the contenders and how the Georgia Senate race — and perhaps control of the chamber — may not be decided until December:

WHO ARE THE PLAYERS?

Most attention in Georgia’s contest has focused on incumbent Democratic Sen. Raphael Warnock and Republican nominee Herschel Walker, whom polls suggest are headed to a tight contest.

Warnock has campaigned on Democrats’ legislative accomplishments like coronavirus relief and infrastructure reforms. Walker has been beleaguered by a variety of critical attention, including claims he exaggerated his business success, as well as successive reports alleging that he encouraged and paid for a woman’s 2009 abortion and later fathered a child with her.

There is, however, a third-party candidate who could affect either major-party contender’s ability to get a majority of votes on election night. Libertarian Party candidate Chase Oliver, seeking to become Georgia’s first LGBTQ candidate elected to Congress, lost a 2020 special election to replace the late Rep. John Lewis.

With an expected close race, it may not take a considerable share of the vote for Oliver, an Atlanta businessman, to force a runoff by keeping Warnock or Walker from getting a majority Nov. 8.

HOW DOES THE RUNOFF WORK?

Under Georgia law, if no candidate gets more than 50% of the vote Nov. 8, the Senate race will go to a runoff four weeks later — on Dec. 6 — between the top two vote-getters.

State and federal runoffs used to happen on different days, but a measure passed last year combines those into a single date. Before this year, runoffs for federal general elections were held nine weeks later.

HOW HAS THIS PLAYED OUT BEFORE?

In 2020, control of the U.S. Senate came down to the twin contests in Georgia, both of which were won by Democrats in runoffs that stretched into the next calendar year. In their 2021 runoff elections, Jon Ossoff and Warnock became the first Democrats to win a U.S. Senate election in Georgia since 2000.

Those victories put the chamber at its 50-50 party-control mark for the next two years, tilting in Democrats’ control thanks to the tie-breaking vote of Vice President Kamala Harris.

Unlike in 2020, only one of those Georgia seats is up this year. In defeating Republican Sen. David Perdue, Ossoff was elected to a full six-year term and won’t be up for reelection until 2026.

The seat Warnock occupies went up for grabs in August 2019, when GOP Sen. Johnny Isakson announced he was resigning because of failing health. Georgia’s governor appointed Kelly Loeffler to temporarily fill the seat, but she had to run in the November 2020 general election to fill the remaining two years of Isakson’s term.

Having won that contest, Warnock is now seeking his first full, six-year term.

WHY DOES THIS MATTER?

With the Senate so closely divided, any of the 35 races on the ballot this fall could decide the 100-seat chamber’s control. The 2021 wins from Warnock and Ossoff gave Biden’s nascent administration a boost in Congress, where the Democratic Senate control, coupled with Harris’ tie-breaking votes, helped cement legislative victories on issues like COVID relief packages, the Inflation Reduction Act and a number of administrative appointments.

Now, whether Democrats can hold on to one of the two Senate seats they won two years ago may serve as a test of whether the longtime Republican stronghold continues a shift to swing state territory, thanks in part to demographic shifts, particularly in the economically vibrant area of metropolitan Atlanta.

In 2018, Democrat Stacey Abrams galvanized Black voters in her bid to become the country’s first African American woman to lead a state, a campaign she narrowly lost. She’s running again this year, in a rematch with GOP Gov. Brian Kemp.

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