Control of the U.S. Senate was still undetermined late Friday, but incumbent Senator Mark Kelly’s win in Arizona tied the Republican and Democratic wins with 49 seats each.

Election officials in the Western state of Nevada said the race there tightened late Friday in favor of the Democratic candidate, Senator Catherine Cortez Masto, against her Republican challenger, Adam Laxalt. If Cortez Masto wins, the Democrats will be in control of the Senate, regardless of the outcome of Georgia’s still-undecided vote, because Democratic Vice President Kamala Harris can cast tiebreaking votes in the 100-member Senate.

Days after Americans voted across the country Tuesday, control of both chambers of Congress — the Senate and the House of Representatives — is still in limbo as final vote tallies have yet to be posted in numerous districts, mostly in Western states.

The Georgia race will be decided in a December 6 runoff election between Democratic Senator Raphael Warnock and his Republican challenger, former football player Herschel Walker. With a third candidate in their contest winning 2% of the vote, neither Warnock nor Walker crossed the 50% threshold required to win the seat.

The latest results from Nevada on Friday evening showed the race getting close in a tight contest between Laxalt, a former state attorney general, and Cortez Masto.

Ballots mailed on Election Day can still be counted in Nevada if they are received by Saturday. Officials in that state have a Thursday deadline to finish counting all the ballots.

Both Nevada and Arizona were working to count a high number of mail-in ballots, which take longer to tally because election officials need to match signatures on mail-in ballots to voter registration rolls.

Election workers in Arizona are also still counting ballots to determine the outcome of the race for governor as well as three competitive House seats.

Kari Lake, the state’s Republican gubernatorial candidate, has accused election officials in Maricopa County, Arizona’s most populous, of deliberately delaying the vote counting to make it look like Democrats are doing better than they actually are.

The Republican chair of the county board of supervisors, Bill Gates, rebuffed the charge, saying staff are working 14-18 hours a day and will continue through the weekend.

“This is how things work in Arizona and have for decades,” he said, adding, “We are doing what we can and still maintaining accuracy.”

In the race for control of the House of Representatives, Republicans edged closer to winning control but have not yet reached a majority of seats.

As of Friday, Republicans appeared to have won 211 House contests in their quest to attain a 218-vote majority in the 435-member chamber. Democrats have won 200 seats, leaving 24 races undecided, according to The Associated Press, as vote counting continues.

In California, results in more than a dozen competitive House districts have yet to be announced.

Republicans say they are confident they will win the House majority even as they voice dismay that the size of their political advantage over Democrats is likely to be far smaller than pre-election predictions that forecast a “red wave” of Republican winners filling the House chamber come January, when the new Congress is sworn in.

If Republicans do take control of the House, it would give them veto power over President Joe Biden’s agenda and the ability to launch investigations into his administration.

Biden on Wednesday characterized his Democratic Party as having done better than expected against the Republicans and announced he will invite leaders of both parties to the White House after he returns from G-20 meetings in Indonesia to discuss how to work together on economic and national security priorities.

Whatever the eventual outcome, Biden said the election, carried out with only minor disputes across the country, was a good day for America.

“Our democracy has been tested in recent years, but with their votes, the American people have spoken and proven once again that democracy is who we are,” he said.

Some information in this report came from The Associated Press and Reuters.