Voting is under way in the southern US state of Georgia in an election that will decide who controls the Senate.
The Republicans currently hold the majority in the upper house but the Democrats are only two seats away from controlling it.
The high-stakes run-off election pits Republican Senator David Perdue against challenger Jon Ossoff, and incumbent Kelly Loeffler against Democrat Raphael Warnock.
If Mr Ossoff and Mr Warnock unseat the Republicans, the Democrats will secure 50 Senate seats, with vice president-elect Kamala Harris giving them the majority with the tie-breaking vote.
If Ms Loeffler and Mr Perdue secure their seats, Republicans will continue to hold the Senate majority they have held since 2014.
If it is a split decision and Democrats grab only one seat, the Republicans will hold a majority at 51-49.
The turnout is reportedly lower than Election Day on November 3 in a state that votes traditionally Republican but flipped for Joe Biden against President Donald Trump by nearly 12,000 votes.
Mr Trump's attempts to undermine that vote and interfere by calling Georgia Secretary of State Brad Raffensperger on Saturday to overturn the result has added to Republican woes in the state.
But historically, conservatives have performed better in special elections and run-offs in Georgia and could still come out on top.
The Democrats are betting on high early voting turnout that could tip the scales as it did in the general election.
More than three million people have voted early in the Georgia run-offs and Democrats have an edge in that category.
A smooth voting process was reported across the state with no major problems, despite a tweet from Mr Trump complaining about the voting machines in one precinct.
A federal judge in Georgia on Tuesday denied another request by he and his legal team for an emergency injunction to decertify the 2020 presidential election results in the state.
This was Mr Trump’s third request to be dismissed by Georgia courts.
While polls will close at 7pm, the final count could be delayed if the results are close and because of mail-in ballots.
Thousands of ballots cast by Georgians living overseas or in the military serving abroad delayed the count in the November 3 election.