ATLANTA (AP) — Georgians cast high-stakes final votes Tuesday in elections to determine the balance of power in the new Congress, deciding Senate runoff elections sure to shape President-elect Joe Biden's ability to enact what could be the most progressive governing agenda in generations.

Republicans are unified against Biden's plans for health care, environmental protection and civil rights, but some have feared that outgoing President Donald Trump's brazen attempts to undermine the integrity of the nation's voting systems might discourage voters in Georgia.

State election officials  reported light turnout  Tuesday morning, including in the deeply conservative northwest region where Trump held a rally Monday night to encourage GOP voters to turn out in force. Wait times at polling sites were "almost nonexistent," averaging about one minute statewide, said Secretary of State Brad Raffensperger.

More than 3 million Georgians had voted early, either by mail or during in-person voting in December. The robust early turnout was expected to benefit Democrats, as it helped Biden in November become the first Democratic presidential candidate to win Georgia since 1992.

"This is history unfolding in Georgia right now," Jon Ossoff, one of Georgia's two Democratic challengers, told reporters outside an Atlanta polling site.

Republicans were counting on a big turnout Tuesday to boost their chances.

"You've got to swarm it tomorrow," Trump told thousands of cheering supporters Monday night, downplaying the threat of fraud even as he repeatedly declared that the state's November elections were plagued by cheating that Republican officials, including his former attorney general and Georgia's elections chief, say did not occur.

Democrats must win both of the state's Senate elections to gain the Senate majority. In that scenario, the Senate would be equally divided 50-50 with Vice President-elect Kamala Harris serving as the tie-breaker for Democrats.

The Democrats secured a narrow House majority and the White House during November's general election.

Georgia's January elections, necessary because no Senate candidates received a majority of the general-election votes, have been unique for many reasons, not least because the contenders essentially ran as teams.

One contest featured Democrat Raphael Warnock, who serves as the senior pastor of the Atlanta church where Martin Luther King Jr. preached. The 51-year-old Warnock was raised in public housing and spent most of his adult life preaching in Baptist churches.

Warnock was facing Republican Sen. Kelly Loeffler, a 50-year-old former businesswoman who was appointed to the Senate a year ago by the state's Republican governor. She is only the second woman to represent Georgia in the Senate, although race has emerged as more of a campaign focus. Loeffler and her allies have seized on snippets of Warnock's sermons at the historic Black church to cast him as extreme. Dozens of religious and civil rights leaders have pushed back.

The other election pitted 71-year-old former business executive David Perdue, who held the Senate seat until his term officially expired on Sunday, against Democrat Ossoff, a former congressional aide and journalist. At just 33 years old, Ossoff would be the Senate's youngest member if elected. He first rose to national prominence in 2017 during an unsuccessful House special election bid.

Even a closely divided Democratic Senate wouldn't guarantee Biden everything he wants, given chamber rules that require 60 votes to move most major legislation. But if Democrats lose even one of Tuesday's contests, Biden would have little shot for swift up-or-down votes on his most ambitious plans to expand government-backed health care coverage, address racial inequality and combat climate change. A Republican-controlled Senate also would create a rougher path for Biden's Cabinet picks and judicial nominees.

"Georgia, the whole nation is looking to you," Biden declared at his own rally in Atlanta on Monday. "The power is literally in your hands."

Despite fears among some Republicans that Trump's baseless claims of voter fraud could depress turnout, the two GOP candidates strongly support him. Perdue on Tuesday said that Trump would "of course" deserve credit if the Republicans won.

"What the president said last night is, even if you are upset about all of that, you've got to stand up with us and fight," Perdue told "Fox & Friends." "We'll look back on this day if we don't vote and really rue the day that we turned the keys to the kingdom over to the Democrats."

Loeffler has pledged to join a small but growing number of GOP senators protesting Congress' expected certification of Biden's victory Wednesday.

"We have to get to the bottom of what happened in this election," Loeffler told reporters while campaigning in the Atlanta suburb of Sandy Springs. "There are too many unresolved, open investigations."

Warnock accused Loeffler of "aiding and abetting" Trump's efforts to overturn his election loss.

"She wants to spend her time trying to take your voice," Warnock told supporters in suburban Marietta north of Atlanta. "We know Joe Biden won Georgia. How many times do we have to count the votes? So what we need now is to get him help."

Democrats have hammered Perdue and Loeffler, each among the Senate's wealthiest members, for personal stock trades made after members of Congress received information about the emerging threats of COVID-19 as Trump and Republicans downplayed the pandemic. None of the trades has been found to violate the law or Senate ethics rules, but Warnock and Ossoff have cast the Republicans as self-interested and out of touch.

Perdue and Loeffler have answered by lambasting the Democrats as certain to to usher in a leftward lunge in national policy. Neither Warnock nor Ossoff is a socialist, as Republicans allege. They do, however, support Biden's agenda.

The Georgia runoffs mark the formal finale to the turbulent 2020 election season and have drawn nearly $500 million in campaign spending to a once solidly Republican state that's now a battleground. The outcome will help demonstrate whether the political coalition that fueled Biden's victory was an anti-Trump anomaly or part of a new landscape.

Biden won Georgia's 16 electoral votes by about 12,000 votes out of 5 million cast in November.

Democratic success will likely depend on a huge turnout among African Americans, young voters, college-educated voters and women, all groups that helped Biden win Georgia. Republicans have focused on energizing their own base of white men and voters beyond the core of metro Atlanta.

In downtown Atlanta, Henry Dave Chambliss, 67, voted for the two Republicans. He said he wants Republicans to keep Senate control to ensure the incoming Biden administration doesn't slide "all the way to the left."

"I'm moderately successful and I know they will come after more of my money which I've earned," Chambliss said. "I was born a Southern Democrat, and I just hope and pray that some moderate voices are heard and things stay more in the middle of the road."

Beverly McDaniel cast her ballot Tuesday morning amid light turnout at a neighborhood center's gymnasium in Atlanta. She voted for both Democrats, saying she believes they would do better dealing with the hardships wrought by the coronavirus.

"Our kids are not fully, fully in school like they're supposed to be and people don't have jobs," said McDaniel, a medical field worker. She said the virus "is taking over where we should have the government taking over instead."

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Bynum reported from Savannah, Georgia. AP journalists Haleluya Hadero and Angie Wang contributed from Atlanta.