I've already said that another debate is useless, 21 is enough.
Barack is fighting against the establishment and the 3 Clinton: Bill, Hillary and Chelsea, while he's campaign alone and holding a town hall meeting alone, the Clinton are campaigning at 3 in 3 different places, so they have a 3 to 1 advantage over Barack. Which means that he needs even much more time to reach people and convince them to vote for him, he doesn't have time for anothe debate, this time must be used for town hall meetings as many as possible, talking directly to voters.
No more debate it's a waste of time, Hillary just stay cool, it's almost over for you, you'll have time to debate with Barack at the end of this process, when he is our nominee.

David