It will be a study in contrasts around age, gender, race, temperament and policy. It will also be the first time in US presidential history that a former courtroom prosecutor will take the debate stage alongside a convicted criminal with the White House at stake.
Vice-President Kamala Harris, the Democratic nominee, has served as a trial lawyer, district attorney and state attorney general in California. Former US president Donald Trump, her Republican rival, has been convicted of 34 counts of falsifying business records to cover up a sex scandal.
For any other candidate on a debate stage, the convictions would be a huge liability. But Trump has repeatedly rallied his base by falsely claiming that the case, and others relating to election interference and mishandling classified information, are bogus and politically motivated. Should the topic arise on Tuesday, he is likely to cast himself as a martyr and also remind viewers that he was nearly assassinated in July.
Harris and Trump have never met before in person and, in the city of Rocky Balboa, are likely to take on the roles of boxer and fighter respectively. Trump, 78, is not known for his discipline, preparation or fidelity to the truth. His debate performances, like his governing style, are typically based on gut instinct rather than considered analysis.
Harris enters the debate with momentum. After she closed out the convention on 22 August, her campaign announced she had raised more than $500m since entering the race. The polling aggregator website 538 shows Harris up by three percentage points in national polls but much tighter races in some battleground states.
