With just three weeks left until polling day on 8 November, the two official nominees will attempt to persuade America they have what it takes to take the top job.
After two bitter clashes on live TV, Wednesday night is their last chance to sway any undecided voters.
Since Trump’s comments about “grabbing” a woman became public knowledge and a variety of women have come forward to complain he sexual harassed them, the Republican nominee has seen his ratings take a hit.
In one poll, Clinton surged ahead by 12 points. Trump is unlikely to come back as a result of this debate, but the world will be watching carefully to make sure that Clinton doesn't fall at the final hurdle.
Expect more probing on the Secretary of State's emails, Trumps's attitude to women, and whether either of them are fit to be president.
This week The Donald has been stepping up his attacks on Clinton and the media, accusing the two of working together to rig the debate.
The businessman tweeted that the contest was “absolutely rigged” by the “dishonest and distorted media” who were putting “stories that never happened into news”.
The election is absolutely being rigged by the dishonest and distorted media pushing Crooked Hillary - but also at many polling places - SAD— Donald J. Trump (@realDonaldTrump) October 16, 2016
Ahead of the debate, Clinton is winning the millennial vote 3-1 according to a new poll from USA Today/Rock The Vote. But will any of the 18-34 age bracket will watch the debate anyway? Campaign analysts are also worried that these young people won’t actually go to the polls on election day.
Some interesting research from Gallup has showed that since the debates began, Democrats have been warming to Clinton, but Republicans have moved away from Trump.
The Dems will be hoping this trend continues when the candidates take to the stage tonight. Chris Wallace of Fox News will be the moderator, and the debate will be split into 15-minute segments.