If he is holding something excessively damning it's quite problematic for for his supports and him, eventually that information would start losing it's value and it will not be a dead-man switch anymore.
This is also a problem because it forces him to dig more and more dirt that can be used as a dead-man switch rather than releasing the information.
You mean the philosophy that has him releasing material with carefully timed consideration to maximize attention to his own pet cause?
http://thehill.com/blogs/ballot-box/presidential-races/29345...
He then says that they would like to get hold of internal documents from the Trump campaign and calls publicly for people to send in things to be published from the Trump campaign.
If there was someone else out there claiming they sent wikileaks material of signifance that was not being published then that would be different.