Polls will shortly close in Alabama as part of a special election that pits Democrat Doug Jones against Roy Moore, a Republican candidate dogged by sexual misconduct allegations.
The race is neck-and-neck despite the state's strong conservative leanings, with Mr Moore denying the claims of eight women who say he harassed them - including one allegation involving a child aged 14.
Polls close at 7pm local time/8pm ET/1am GMT, with results expected to start coming in soon afterwards.
And speaking at a rally on the eve of the election last night, Mr Moore told supporters: "If you don't believe in my character, don't vote for me." Many of his followers simply don't believe the abuse allegations or say they have been blown out of proportion, and he retains the support of the Republican party and the President, Donald Trump.
Follow the latest live updates on the special election below
With 91 per cent of results in - the race is called - Doug Jones has been elected to the Senate - beating Roy Moore.
With more than 85 per cent of the votes counted, Doug Jones has just taken the lead - but the vote is far too close.
At his event in Montgomery, Mr Moore shook hands with supporters after they chanted, "Judge Roy Moore." He then left to watch returns in another room.
His campaign manager told the crowd that Mr Moore would soon have the new title of senator.
With 75 per cent of votes in, Mr Moore leads by 50.7 per cent to 47.9 per cent. But it is still too close to call.
With more than 50 per cent of votes counted, Mr Moore is leading 52.7 per cent to 45.9 per cent.
Roy Moore has arrived at his election night party in Montgomery has is greeting supporters, while Doug Jones has arrived at his event at the Sheraton Hotel in Birmingham.
With 40 per cent of the vote in, Mr Moore is still leading, but the vote is close.
We now have more than a quarter of the results in, with Mr Moore holding a 51 per cent to 47 per cent advantage - but it is too close to call
Senate Republicans plan to convene a meeting Wednesday morning to discuss their next steps if Roy Moore wins the Alabama Senate race
With about 20 per cent of precincts repo, Mr Moore holds a slight advantage with 51.3 per cent to Mr Jones 47.4 per cent.
CNN are quoting two Moore campaign officials who say Mr Moore is working on only one speech and one speech only.
“Tonight is an opportunity for the Judge to call America back to her foundational principles regardless of what happens in the election,” a campaign spokesman told the network.
So, some very early numbers - with less than 1,000 votes counted - have Doug Jones in the lead. But there is a long way to go.
According to exit polls, the breakdown of the electorate is 65 per cent white, 30 per cent black and 3 per cent Latino.
The Jones campaign was looking for anything about 25 per cent when it come to black turnout.
However, an apparent higher turnout overall may negate that target for the Jones campaign.
However, if you are in line to vote you are allowed to stay and do so.
Polls have now closed
Polls are set to close in five minutes.
Alabama's Secretary of State John Merrill said preliminary estimates show a higher voter turnout for this special election.
Earlier, Merrill had predicted a 25 per cent voter turnout. He said he still felt "comfortable" with that number, but it could maybe be higher.
"We think that that's going to end up being the number. It could be a little bit higher. We've seen some numbers that have been a little bit higher in certain aspects of voting throughout the state, than in other areas. But some areas have underperformed," Mr Merrill said.
He added that "a lot" of the absentee ballots have already been recorded, and there were more absentee votes than usual.
According to the CNN exit poll data, 49 per cent of voters said they believed the allegations against Roy Moore were definitely, or probably true, but 55 per cent said it was not an important factor in deciding their vote.
Mr Moore has denied the allegations.
Randall Woodfin, the newly elected mayor of Birmingham, Alabama and a first-term Democrat, told CNN's Wolf Blitzer that Roy Moore was a "threat to integrity and decency, not just for Alabama but for our country."
There are reports of high turnout in both rural areas and major cities - both campaigns seem to be confident mood about what that means for their chances. Mr Moore has a strong rural support base, while Mr Jones does better in cities.
But at his own rally on Monday night Mr Jones said the election was a referendum on "who we are and what we're going to tell our daughters". He was joined by basketball star Charles Barkley, who said it was "amazing" Mr Moore was still in the race and the state risked "looking like idiots to the nation".
Mr Jones, for his own part, has been attacked as a liberal who would not properly represent a state that hasn't elected a Democrat senator for 30 years.
Mr Jones acknowledged in Montgomery: "Look, I'm not going to be the senator that everybody in the state can agree with 100 per cent of the time." But he added: "They'll know I'm somebody that will sit down with them. I will learn from them. ... I will try to be the public servant I think a US senator ought to be."
Tuesday's vote is being held to find a replacement for Jeff Sessions, who was selected as Attorney General by President Donald Trump.
Doug Jones has told supporters that his campaign is a chance to be on the “right side of history for the state of Alabama.”
“Judge Moore has been consistently wrong about the Constitution,” Mr Jones said to reporters after casting his ballot at a Baptist church in Birmingham. “I don't think Roy Moore is going to win this election.”
If Mr Jones wins on Tuesday, Republicans would control the Senate by a slim 51-49 margin, giving Democrats momentum ahead of the November 2018 congressional elections, when control of both chambers of Congress will be at stake.
Poster Comment:
Trump's endorsement was the kiss of death for Roy Moore.
