whatever undecided voters there may be are going to want to see if the candidates match the hype. Hillary is in an impossible position. She can't deliver. She can debate and lose or chicken out and lose harder.
We know that even if Her Thighness shows up at a debate the Left-Wing Media group sponsoring that debate will make hard questions for her off limits. If Trump tries to bring those up the moderator will try to shut him down. Like Trump and Bernie have said “...the system is rigged...”