Mississippi voters are deciding a racially charged election that has dredged up the Deep South state’s ugly past.
In the last Senate contest of the mid-term elections, white Republican Cindy Hyde-Smith faces an unexpectedly tough challenge by black Democrat Mike Espy.
The vote tightened after Ms Hyde-Smith was recorded telling a supporter she would happily attend a public hanging.
Nevertheless she is expected to win in the staunchly Republican state.
On Monday, several nooses were found at the Mississippi capitol in Jackson in an apparent protest against the tenor of the campaign.
Signs alongside the ropes urged voters to elect “someone who respects the lives of lynch victims” and “remind people that times haven’t changed”, according to local media.
The election became more competitive after a video emerged earlier this month of Ms Hyde-Smith telling a supporter: “If he invited me to a public hanging, I’d be on the front row.”
The senator’s comment evoked the lynching of African Americans in a state whose past is rife with racial violence.
According to the National Association for the Advancement of Colored People (NAACP), Mississippi had the highest number of lynchings in the nation from 1882 to 1968.
Mr Espy condemned his rival’s comment as “reprehensible”; Ms Hyde-Smith maintained there was no “negative connotation”.
The Democrat has himself come under scrutiny for his 2011 lobbying work in the Ivory Coast, whose former despot Laurent Gbagbo is on trial at the International Criminal Court.
Mr Espy was agriculture secretary under President Bill Clinton, but resigned under a cloud of corruption allegations, on which he was later acquitted.
Controversy fuels turnout
By Chris Buckler, BBC News, Oxford, Mississippi
“They’re fired up.”
That was the view of polling station staff in Oxford, Mississippi, where a long line of voters greeted them as they opened up this morning.
Everyone here believes that Cindy Hyde-Smith’s comments have helped today’s turnout.
And that’s true on both sides.
In a state where racially motivated lynchings are still a source of shame, Democrats have expressed outrage that she would even joke about a “public hanging”.
Ms Hyde-Smith’s team are trying to present the huge amount of media coverage about her comments as an attempt by Democrats to twist her words – and a cynical ploy to steal what should be a Republican safe seat.
They also point out that her Democratic opponent Mike Espy is himself no stranger to controversy.
The difference might simply be who is most “fired up”. This run-off election is being held between Thanksgiving and Christmas in the wake of mid-term elections that attracted extraordinary interest.
So far, however, controversy is proving to be a very good antidote for voter fatigue.
Ms Hyde-Smith, meanwhile, was further criticised when photos surfaced of her posing at the home of Confederate President Jefferson Davis, with the caption: “Mississippi history at its best.”
A video of Ms Hyde-Smith – who would be the first ever US congresswoman from Mississippi – apparently encouraging voter suppression also emerged on Twitter.
That recording showed the senator saying there were some liberals “who maybe we don’t want to vote – maybe we want to make it just a little more difficult [to vote]”.
Her campaign later said the comment was a joke and the video had been “selectively altered”, the Washington Post reported.
At a recent debate, Ms Hyde-Smith gave a qualified apology to anyone she had offended, while adding that opponents had “twisted” her words “as a political weapon”.
President Donald Trump travelled to Mississippi on the eve of the vote to campaign for Ms Hyde-Smith.
“I know her, and I know she apologised, and she misspoke,” the Republican president told reporters on his way to the southern state.
He painted Mr Espy as a far-left ideologue who would “rather protect illegal aliens than people who live in Mississippi”, and questioned how he “fit in with Mississippi”.
So could a Democrat win?
Mr Espy would become the first black senator since the Reconstruction era following the US Civil War.
His campaign has pushed the idea that electing Ms Hyde-Smith would stoke a lingering view of Mississippi as a racist southern state.
“We can’t afford a senator who embarrasses us and reinforces the stereotypes we’ve worked so hard to overcome,” one ad for the Democrat said.
Mr Espy would need to overwhelmingly win the black vote and a substantial number of white voters to unseat his Republican opponent.
Why is the election still unresolved?
After Republican Senator Thad Cochran resigned in April, a special election for Mississippi’s US Senate seat was arranged.
Under the state’s law, if no candidate wins over 50% of the votes, a runoff election must take place.
On 6 November during the mid-term elections, both Ms Hyde-Smith and Mr Espy received about 41% of the vote.
Polls in the state close at 20:00 local time on Tuesday, with results to follow soon after.
If Republicans hold on to the seat, their US Senate majority would be extended to 53-47.