I think the point is that when you get a guy like Perot who essentially ends up pulling support from one camp, then you have a credible threat to hold over the head of a candidate that you could support in other cases. Remember, Perot was a one issue guy: NAFTA. He talked the tax thing, but the anti-NAFTA position appealed to a lot of "Reagan Democrats" who had been voting Republican up till then.
Just my opinion.