Tell Preibus that you pledge to run a third party candidacy if even one state GOP blocks you from the ballot.
My thoughts, too. Pledge with conditions.
Good, let him. Better he go 3rd party now and flame out sooner rather than later.
There is no constitutional right for the Republican Party to accept anyone, and especially none that requires any political party to allow a person to use their infrastructure only to see them run a spoiler 3rd party campaign or not back the eventual nominee.
Let "the Donald" go 3rd party, force him to spend his own money and let him implode his campaign long before a general election before he can do any actual damage to the actual Republican nominee.