He can't. There are no viable third parties. He tried in 1988 and could not get on the ballot.
Write in campaigns barely work because they require people write!
Besides, what Dr. No's campaign is about fits with the direction the Republican Party said it wanted to go, back to it's roots. Based on the individual rights of the Constitution. That's why the Republicans can't stand him!!!
As I've said before, he is the ONLY one that CAN run on his record, and not blink.
Look at his conrtributors, it's a good indication who supoports him.