I don't know, but I believe GG's answer. Up until election day, I don't see any reason why a runner up or a Vice Presidential candidate would have any rights. The matter is not addressed in the Constitution. The party would have to replace the nominee as they see fit, I think, and each party may have its own written rules on the subject. The election date could theoretically get rescheduled by act of Congress, as well, so long as they could still meet the inauguration deadline.