Kamala Harris and Donald Trump were poised to face off in a potentially game-changing televised debate Tuesday in Philadelphia, less than two months ahead of the knife-edge U.S. presidential election.

The stakes could hardly be higher for the Democratic vice president and Republican former president, with tens of millions of American voters expected to tune in at 9 p.m. to watch their first and possibly only debate.

A single zinger or gaffe could tip the balance of one of the most dramatic White House races in U.S. history, with the two rivals neck-and-neck in the polls ahead of the Nov. 5 vote.