ATLANTA (AP) — In an election where control of the U.S. Senate could be on the line, Georgia is the only state with both Senate seats on the ballot — two opportunities for Republicans to hold their ground; two opportunities for Democrats to make gains.

Republican Sen. David Perdue faces Democrat Jon Ossoff in a race that public polling has shown to be very close. In the other race, Republican Sen. Kelly Loeffler faces a crowded field that includes GOP Rep. Doug Collins and Democrat Raphael Warnock in a special election for the seat Loeffler was appointed to 10 months ago.

Democrats haven't won a Senate race in Georgia in two decades. But ongoing population growth around Atlanta and shifting demographics that have made the state less white — along with dissatisfaction with President Donald Trump in the suburbs — have helped fuel hope among Democrats that the state is in play.

There's a chance both races could stretch into next year, with runoffs to be held on Jan. 5 if no candidate surpasses 50% of the vote in Tuesday's election.

Both sides have poured huge amounts of money into the races, and record numbers of people cast ballots early, with some voters facing hourslong lines. Georgia has also seen a large increase in absentee ballots cast by mail.

Election officials were seeking to avoid a repeat of the June 9 primaries when poll worker shortages, coronavirus restrictions and trouble with new voting machines led to chaos and long lines at some polling places, especially around Atlanta.

Perdue, a former business executive and a close ally of Trump, faces Ossoff, a media executive who launched his political career with an unsuccessful 2017 run for Congress. Their race has been characterized by sharp attacks but relatively moderate political positions.

Perdue has sought to cast Ossoff as backing a “radical socialist agenda,” while Ossoff has portrayed Perdue as a “corrupt” Washington insider.

Loeffler, a super-wealthy businesswoman, and Collins, a four-term congressman who is one of Trump's most visible defenders in the House, have been locked in a battle for voters from the conservative base of the GOP. Meanwhile, Warnock, pastor of the Atlanta church where Martin Luther King Jr. preached, has been largely able to float above the fray after consolidating support among Democrats.

With a runoff in the race highly likely, the bitterly personal tone of Loeffler and Collins’ attacks could make it difficult for the candidates — and their supporters — to mend fences in time for the January runoff, University of Georgia political scientist Charles Bullock said.

“Her challenge would be to simply get Republicans back behind her,” if Loeffler advances to a runoff, Bullock said. “That’s a real risk.”

Joey Odom of Savannah voted early for Perdue, saying his support for the coastal city’s seaport has helped the local economy. A 58-year-old sales representative for a manufacturer, Odom said he typically votes Republican and supports Trump. He gave Trump and Perdue high marks for their efforts to reopen businesses during the coronavirus pandemic.

“I’m a little more on the side of opening the economy back up where it makes sense,” Odom said. “I feel for some of the states that are still essentially shut down while ours is up and running to an extent.”

In Decatur just outside Atlanta, Linnea Pace cast her vote early for Ossoff. The 57-year-old said she didn’t vote for any Republicans.

“I live in a Black, middle-class neighborhood. I haven’t seen any Republican come into my neighborhood and ask me what is going on,” Pace said, noting that Ossoff had visited her church.

Pace also said she believes Perdue sold stock to benefit himself when he first learned the coronavirus could devastate the U.S. economy.

“He knew that pandemic was coming,” she said.

Early in their campaign, Perdue and Loeffler were both among senators whose stock trades, made just before the virus caused a downturn in the markets, came under scrutiny. Both denied any wrongdoing, saying the trades were made by independent advisers and that they were ultimately cleared by a Senate Ethics Committee investigation.

Regardless, their opponents have made the stock trades a central line of attack. Collins has accused Loeffler of “pandemic profiteering,” while Ossoff has accused Perdue of having “profited from the pandemic while he downplayed the risk.”

Top Democrats in the race outraised the Republican incumbents, but the Republicans were also buoyed by outside spending.

More than $160 million has been spent on television and digital advertising by candidates and outside groups in both races.

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Bynum reported from Savannah, Georgia.

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Find AP’s full election coverage at APNews.com/Election2020.