Officials are counting ballots in two pivotal runoff elections in the southern US state of Georgia that will determine the balance of power in Congress. President-elect Joe Biden's Democratic Party is hoping to gain control of the Senate for the first time in years.
Polling stations have closed, and many people opted for advance voting due to the pandemic.
The results may not be known for several days because of the high number of mail-in ballots.
If Democrats win both races, it would allow Kamala Harris to cast the deciding vote in the chamber as vice president.
If Republicans win either seat, the party would retain a slim majority and could block Biden's legislative agenda.
The Democrats maintained control of the House in the November elections.
At a rally in Atlanta on Monday, Biden once again criticized President Donald Trump's handling of the coronavirus and pledged to speed up vaccinations.
Trump also spoke at an event in the state, attacking Biden and stoking fears over the Democrats' immigration policies.
This comes as members of Congress prepare on Wednesday to certify the outcome of another race -- the November presidential election. A growing number of Republicans have suggested they will raise objections to that result.