Comment: mixed stories about 3rd party

Can someone please explain to me if it is or isn't possible for RP to go third party at this point. I'm not asking if he is willing, just that if it is possible. I keep hearing from some that it is, and from others that it is not. There is nothing more that I would like if he doesn't get the nomination, but I was under the understanding that the cut off date is passed and that any other avenues, such as AE, have been closed. Not arguing one way or another, but would like to know if its at all even possible at this point. I am guessing no.