The unresolved 2022 House and Senate races that will determine control of Congress

Washington — After Democrats' surprisingly robust performance in the 2022 midterm elections, the battle for control of Congress remains unsettled with a handful of Senate races and several dozen House contests still up in the air.

According to CBS News estimates, four Senate races were unresolved as of Thursday, and three of those will determine which party ultimately controls the upper chamber: Arizona, Nevada and Georgia. (The winner in Alaska's race is also unclear, but because of how the state chooses its senators, the top two candidates are both Republicans, meaning the result won't change the partisan makeup of the Senate.)

Republicans need 51 Senate seats to control the chamber. Democrats, however, need only 50 votes, since Democratic Vice President Kamala Harris casts tie-breaking votes in the event of a 50-50 split. With Democrats currently projected to control 48 seats and Republicans projected to hold 49, the party that wins two out of the three races in Arizona, Nevada and Georgia will gain control of the Senate. 

The outcome of the Georgia race won't be known until after a runoff election between Democratic Sen. Raphael Warnock and Republican Herschel Walker on Dec. 6. CBS News characterizes the overall Senate battle as a toss-up.

The fight for the House, meanwhile, appears favorable for the Republicans, who needed to flip just five seats to overcome Democrats' thin majority coming into the election. CBS News estimates the GOP will control at least 210 seats in the lower chamber, compared to at least 200 for the Democrats. Both parties are still short of the 218 seats needed to secure a majority.

Here's a look at the remaining races that will ultimately determine control of Congress, as of Thursday:

The Senate

Arizona

CBS News characterizes the race between Democratic Sen. Mark Kelly and GOP challenger Blake Masters as leaning in Kelly's favor. Nearly a quarter of the state's votes have not yet been counted, including 27% of the votes in Maricopa County, the state's most populous. Kelly's lead has been shrinking as more votes continue to be counted, a process that could take several days to complete.

Georgia

Neither Warnock nor Walker reached the 50% threshold needed to avoid a runoff election, with Warnock winning 49.6% of the vote and Walker taking 48.3%. Libertarian candidate Chase Oliver won 2.1%.

Both parties have already begun raising money to fund the Dec. 6 showdown in the Peach State, which would be decisive if Democrats and Republicans split Arizona and Nevada. Warnock won a runoff after the 2020 election to win his current seat.

Nevada

The race between Republican Adam Laxalt and Democratic Sen. Catherine Cortez Masto is characterized as a toss-up, according to CBS News estimates. Laxalt is leading Cortez Masto, the incumbent, by more than 15,000 votes. 

However, roughly 99,000 votes remain to be counted in Clark County, the state's largest and a Democratic stronghold. Cortez Masto has won 51% of the 608,429 votes already counted in Clark County, compared to Laxalt's 46%. The count could last until next Thursday, one election official said.

The House

The race for the House leans in Republicans' favor, according to CBS News estimates, which show the GOP ultimately controlling at least 210 seats, compared to 200 for the Democrats. 

Of the races in which CBS News has projected a winner or a candidate has conceded, 15 seats have switched from Democrat to Republican, while seven have switched from Republican to Democrat. Republicans flipped four seats in New York alone.

In one notably close race in Colorado, GOP Rep. Lauren Boebert trails Democrat Adam Frisch by just 64 votes, out of 313,433 votes counted.

Fifty-one House races remain unresolved, 18 of which are in battleground districts, including four in California:

Aaron Navarro contributed to this report.