Hillary Clinton and Donald Trump will take to the stage in Las Vegas later for the final debate in an increasingly bitter race for the US presidency.
Polls show Mr Trump is losing in key battleground states after facing a slew of sexual assault allegations.
But Mrs Clinton remains unpopular with many US voters and has faced more bad headlines about her use of a private email server.
Most Americans will cast their votes on 8 November.
Millions are expected to tune into the third and final debate at the University of Nevada, Las Vegas which gets under way at 21:00 EDT (01:00 GMT) and will be moderated by Fox News journalist Chris Wallace.
The two candidates will discuss six topics: national debt and health and social benefits, immigration, the economy, the Supreme Court, foreign flashpoints and their fitness to be president.