The results of the runoff elections will determine which party controls the U.S. Senate -- and voters are nearly split on their preference, preliminary exit poll results show.

Forty-nine percent prefer Republican Party control, while 48% prefer control by the Democrats, based on the preliminary results.

The GOP needs either seat to retain control of the Senate, while the Democrats need both to win control.

Voters also were nearly split in their vote for president in the general election, based on the preliminary results -- suggesting that Democrats were holding their own in runoff turnout.

Voters in the race between Democrat Raphael Warnock and Republican Kelly Loeffler report having voted a dead-even 47%-47% Donald Trump-Joe Biden, preliminary results show. In the contest between Democrat Jon Ossoff and Republican David Perdue, it’s about the same -- 48%-47% Trump-Biden, based on preliminary results.

-ABC News' Gary Langer, Christine Filer and Steven Sparks

Polls across the state are closing as a flurry of advocates urge those who haven't voted and are still standing in line to stay past 7 p.m. and make sure their ballots are cast.

Georgia voters also had until 7 p.m. to return absentee ballots in drop boxes across the state.

A few polling precincts have gotten judicial extensions to be open past 7 p.m.: one in Gwinnett County, two in Columbia County, one in Tift County and two in Chatham County. There was also an accident near a polling place in Ware County that may lead to a judicial order extending poll closing time, said Gabriel Sterling, the state voting system implementation manager.

Sterling, in the most recent election update, described the day overall as "smooth voting, steady voting."

He said the state was getting reports of longer lines forming in Houston, Cherokee, Paulding and Forsyth counties with wait times approaching an hour, but not going over.

-ABC News' Quinn Scanlan

Former President Barack Obama tweeted to Georgia voters that while state polls close at 7 p.m., they should stay in line if they've arrived at their polling location in time.

"You have the right to vote, no matter how long it takes," Obama tweeted.

Some precincts in the state will be open past 7 p.m. due to court orders.

Obama joined a virtual rally for Democratic candidates Rev. Raphael Warnock and Jon Ossoff earlier this month and has appeared in digital ads for both candidates. On Monday, the former president tweeted "the stakes could not be higher" in promoting the runoff elections.

A majority of voters in Georgia's Senate runoffs think the presidential election was fair, preliminary exit poll results show.

More than half -- 56% -- of voters think the presidential election in Georgia was conducted fairly, while 41% do not, according to the preliminary results.

President-elect Joe Biden defeated President Donald Trump by nearly 12,000 votes in Georgia. Trump repeatedly has made unsubstantiated claims of voter fraud in Georgia, among other states.

Most voters also express at least some confidence in the current runoff elections. Seventy-three percent are very or somewhat confident that votes in the runoffs will be counted accurately, while 26% are not very or not at all confident, according to the preliminary results. This is down from a similar question in November, when 85% were very or somewhat confident that votes in their state would be counted accurately.

-ABC News' Gary Langer, Christine Filer and Steven Sparks

More than 3 million voters in the Georgia runoff elections cast their ballots early -- 1,018,381 by mail and 2,074,994 early in-person -- according to Georgia Votes, already a record-setting figure for runoff elections.

The total early vote so far also includes 123,079 who did not participate in November's general election -- which is 35,000 more votes than the margin that separated Sen. David Perdue and Jon Ossoff the first time around, when the incumbent Republican edged out his challenger by just over 88,000 votes. Sen. Kelly Loeffler and Raphael Warnock were competing in a jungle primary in which the large field diluted their vote shares.

The secretary of state's office won't have Tuesday's in-person turnout numbers until at least 1 p.m. on Wednesday when counties are required to report how many ballots they received Tuesday in order to calculate the number of outstanding ballots. It may take days for the final results to become available depending on how close the races are.

Republicans are relying on high Election Day turnout, believing close to a million votes on Tuesday is likely their path to victory. At a rally in Dalton on Monday night, President Donald Trump signaled how many votes Republicans are eyeing: "I guess we have to get over a million votes tomorrow, right, Kelly? Over a million. All right. That's a lot of votes, Kelly, but we'll do it."

-ABC News' Quinn Scanlan, Kendall Karson and Meg Cunningham