Voters hoping to immediately know who will control the U.S. Senate in the next Congress may be in for a shock on election night as it could take days or weeks to tabulate results in key states.

Some election officials are already warning about delays.

"We will not have final results on election night," a spokesperson for Nevada Secretary of State Barbara Cegavske told Fox News Digital.

"Voters, candidates and the public should not expect complete results on election night," Pennsylvania Acting Secretary of State Leigh Chapman said in a recent media briefing.

"We understand that voters, candidates and the media want election results as soon as possible," Chapman said. "But counting all the eligible votes and reporting the results take time."

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Leigh Chapman, Pennsylvania acting secretary of state, speaks with reporters

Pennsylvania Acting Secretary of State Leigh Chapman speaks with reporters about Pennsylvania's 2022 elections, warning that it will take days or more for election results to become clear. (Pennsylvania Department of State)

Chapman's office said the delay is related to rules in Pennsylvania that do not allow its mail-in ballots to pre-processed until 7 a.m. on Election Day. This means the process of removing the ballots from envelopes and scanning them will likely last well past election night.

With the Senate race between Republican Dr. Mehmet Oz and Democrat Lt. Gov. John Fetterman expected to be very close, R Street Institute resident elections fellow Matt Germer told Fox News Digital that the suspense could drag on for days at least.

"It's possible that Pennsylvania takes a good while," Germer said. "They had a problem in 2020 where so many more people were sending in their ballot by mail. But they, the election administrators, weren't allowed to pre-process those ballots. … What that meant was they just had this giant glut of mail-in ballots and a ton of administrative work to do."

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"I'm expecting that it will once again make for a slow night for election results in Pennsylvania," he said.

In Nevada, mail ballots can be postmarked as late as Election Day. That means valid votes could continue coming into election officials for several days after Election Day. If the race between Sen. Catherine Cortez-Masto, D-Nev., and Republican Adam Laxalt is close, Germer said, "we won't have necessarily a clear result in Nevada either for perhaps a week."

John Fetterman, Mehmet Oz

Pennsylvania Senate candidates John Fetterman, left, and Mehmet Oz participate in a debate on Oct. 25, 2022, in Harrisburg, Pennsylvania. (NewsNation)

"Counties started processing and counting on Oct. 24th. They have until Nov. 12th to receive all mail ballots, Nov. 14 to cure signatures and Nov. 18 to certify results," said the spokesperson for the Nevada secretary of state.

Unlike Pennsylvania, Arizona does allow processing of mail-in ballots before Election Day, something Germer said will likely speed up that state's ability to deliver a result. However, Cochise County will count all of its ballots by hand, which could delay a final projection.

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But the state that may cause the biggest delay in knowing the Senate majority is one that could very well have a result on election night: Georgia.

That's because Georgia law requires its U.S. Senate candidates to win at least 50% of the statewide vote to win a general election. In a very close race between Sen. Raphael Warnock, D-Ga., and GOP challenger Herschel Walker, a few percentage points of the vote going to libertarian Chase Oliver could hold both under 50% and rigger a runoff.

"Once again, the balance of power in the Senate may come down to a Georgia runoff," Germer said.

Oliver and Warnock

Sen. Raphael Warnock, D-Ga., shakes hands with libertarian challenger Chase Oliver at a Georgia U.S. Senate debate. If Oliver garners just a few percent of the general election vote, he could hold both Warnock and GOP candidate Herschel Walker under 50%, triggering a runoff. (Ben Gray/Associated Press)

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This year, the general election runoff in Georgia will be held on Dec. 6, as compared to its Jan. 5 date in the 2020 cycle.

In Georgia, a recently-passed election law will mandate that all precincts report how many uncounted votes they have by election night. A spokesperson for Georgia's Secretary of State office told Fox News Digital that means observers will have a "clear understanding of how many votes exactly [are outstanding] and in what counties."

Georgia's will also likely report early and absentee votes first, the spokesperson said. 

Elsewhere, Alaska could take some time to tabulate its Senate results due to its size and its ranked-choice voting system. It took more than two weeks to calculate the winner in a recent House of Representatives special election using that same system.

But Alaska's top Senate candidates are Sen. Lisa Murkowski, R-Alaska, and Republican Kelly Tshibaka, who is challenging the incumbent from the right. Therefore, that race won't impact the balance of power in D.C.

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Other battlegrounds, including Ohio, Wisconsin and New Hampshire, have a record of delivering results on election night. It's not expected they'll have issues doing the same this year.

Even if some states do take time to figure out who the winner is due to inefficient systems, Germer said, voters shouldn't assume there's fraud.

"It can be frustrating as a voter to not have resolution immediately, especially in our culture now," he said. "We can rest assured that the processes that we have across the country will give an accurate result."