ATLANTA (AP) — Campaigns and outside groups are making a final push to turn out election-weary Georgians whose votes will determine control of the U.S. Senate.

More than 2.3 million people — nearly half the turnout of last month’s presidential election — had already cast their ballots early, in person or by absentee ballot, by Tuesday morning.

With margins in the Jan. 5 runoffs expected to be tight, the campaigns for Republican U.S. Sens. David Perdue and Kelly Loeffler and Democratic challengers Jon Ossoff and Raphael Warnock are all focused on mobilizing voters.

“We want to run through the tape. We don’t want to leave anything for granted," said Jessica Anderson, executive director of Heritage Action, a grassroots conservative organization that has volunteers and staffers knocking on doors, making phone calls and sending text messages.

Roshan Mody is the co-founder of Plus1Vote, which focuses on getting young people out to vote on climate change, social justice and voting rights. He told progressive activists Monday during an online briefing that it’s going to come down to turnout.

“All the signs are good,” he said of Democrats' chances. “But a blowout is less likely than us kind of going over the edge by 10-20,000 votes.”

In the nearly two months since the general election in November, Georgians have been inundated by radio and television advertisements, mailings, calls, text messages and even hand-written notes from out-of-state residents urging them to vote.

Runoff elections historically draw a much lower turnout than general elections, and in Georgia they have favored Republican candidates in the last decade or so. But in this unique election — with national attention, money pouring in and control of the Senate at stake — the normal rules don't seem to apply.

Rather than dropping dramatically, early voting for the runoff is only about 20% lower than the early turnout at the same point before the general election, though missed days over Christmas and other key differences make a direct comparison difficult. Voters don't register by party in Georgia, but experts who have been tracking early voting data say the high turnout, particularly among African American voters, and the continued engagement of younger voters is a good sign for the Democrats.

“These are the numbers that the Democrats need in order to be able to win the election," said Michael McDonald, a University of Florida professor who tracks vote counts for the U.S. Elections Project. “It doesn’t mean that they are going to win. It’s just the numbers they would want to see if they are going to win.”

But McDonald and others are quick to say that the election results are likely to be very close, and there's too much uncertainty to draw reliable conclusions from the early voting data about which candidates will win.

While early voting trends so far may seem to favor Democrats, Republicans typically have higher Election Day turnout and they could also make gains in the final days of early in-person or absentee voting, McDonald said. There are also wildcard factors like the weather — though the current Election Day forecast is mild and dry across the state — and possible complications caused by the coronavirus pandemic, he said.

In-person early voting ends statewide on Thursday, though some counties observe New Year's Eve as a holiday so Wednesday will be their last day. Absentee ballots can be returned by mail or in drop boxes to be counted as long as they're received by 7 p.m. on Election Day.

Perdue and Loeffler both failed to win a majority of votes in the general election last month, forcing the runoffs.

After a bitter fight during the general election between Loeffler and third-place finisher GOP U.S. Rep. Doug Collins, Republicans needs to focus on making sure Collins voters support Loeffler for the runoff, Emory University political science professor Bernard Fraga said. They also need to stress the importance of voting despite repeated claims from President Donald Trump and his allies that the presidential election was rigged and marred by fraud.

“Republicans can’t afford to throw away any votes,” Fraga said. "I think this just adds to the pressure on Trump to make a very forceful push to his supporters regarding the importance of this election and the importance of their participation in this election.”

The president already held a rally earlier this month in Valdosta, in south Georgia, and he's set to hold another Monday in Dalton, a Republican stronghold in the northwest corner of the state. Vice President Mike Pence and other high-profile Republicans have also traveled to Georgia.

President-elect Joe Biden and Vice President-elect Kamala Harris are among the Democratic heavy hitters who have come to help mobilize voters for Warnock and Ossoff.

In the final days before the election, Democrats need to work on turning out Latino and Asian American voters, Fraga said. Participation by both groups surged in the general election, but they are less consistent voters and will need extra mobilization to turn out in the runoff, he said. A continued focus on younger voters is also critical.

“It looks a lot better for Democrats now than anyone would have predicted based on the historical record," Fraga said. “I think the question is whether it’s enough and the next few days are going to be key for seeing whether the group-level differences in turnout are suggestive of a pattern that favors Democrats.”

So far, very few of the runoff voters are people who didn’t vote in general election, Fraga said.

“If we assume that very few people are changing their minds about which party they’re going to vote for in the runoff, then much of the electoral landscape has already been baked in in Georgia and it’s really a story about turnout instead of changing people’s minds,” he said.