The first presidential debate of the US general election is often the most treacherous - especially for the candidate who steps on stage with the presumed advantage.
Which is why Democratic nominee Hillary Clinton, the one in that position this time around, knows not to take anything for granted.
Tomorrow's 90-minute faceoff is projected to have the biggest audience ever with estimates that more than 100 million people will watch.
"You can't really win an election in a debate, but you can lose one," said Brett O'Donnell, a communications consultant with long experience coaching Republican presidential candidates.
"The first debate is the most important of all the debates, and it definitely has the most potential to harm."