The debate, which is expected to be watched by tens of millions of Americans, could draw a record number of viewers when it kicks off at 9:00 pm.
Clinton, 68, enters the fray as a polished former secretary of state and ex-senator, who after almost 40 years of public service is well versed on the issues.
Trump, a 70-year-old billionaire and former reality TV star, is good on his feet, and unpredictable — more comfortable in the limelight than on issues.
As many as 90 million people are expected to tune in as the pair face off at Hofstra University in New York six weeks before the November 8 election.
The debate is being held one day after a Washington Post-ABC News poll revealed that Clinton’s slim advantage over Trump from last month has evaporated.
She is tied with Trump at 41 percent among registered voters, with Libertarian candidate Gary Johnson at seven percent and Green Party candidate Jill Stein at two percent, according to the poll.
In a two-way match-up, Trump and Clinton were even at 46 percent of registered voters. The survey showed a statistical tie among likely voters as well.