Is Donald Trump really doomed if the republican establishment puts out a 3rd party candidate?

When people are asked questions about what would happen if there was a 3rd party candidate set up by the GOP elite they will say something like “The same thing that happened with Ross Perot will happen.” While that may be true I believe something else may happen. Back in 1980 the Republican primary was between Ronald Reagan. George H. Bush. And John B. Anderson.