I was using Perot as an example of trying to get to the Presidency on your own without using the democrat or republican apparatus.
What his motivations were to run for president is another matter.
Functionally, what happens is that the two parties change fundamentally over a period of time, but there's usually a face you can attach to the breakover point in the change. McGovern for the Rats, Reagan for the Pubbies.
Since the Republicans in the 1800's no "new" political party has managed to do anything other than ensure the defeat of the party closest to them in attitude. Teddy Roosevelt did this with the Bull Moose party, Nader seriously helped Bush last year, etc. I think the primaries is where you move political thought, and that's one of the reasons that people are more ideologically polarized during the primaries. Your overall point of multiple political parties within the two major parties is very valid. When parties split off to form their own, such as the greens or the libertarians, they generally fail.
These third parties are generally formed by people who are willing to give up winning elections to make a point. Second, they're generally formed by people who are unwilling to hammer out deals. The reason Pat Buchanan left the Pubbies was because he was too inflexible to modify his politics to create a large enough coalition to win. Whether he was right or not on every issue, it really doesn't matter. He won't get elected.
Second, the parties are generally formed by people with confrontational personalities. I tend towards libertarian beliefs, but many of the libertarians here at FR p!ss me off, even when making points I agree with. "You WODers little tyrants can go back to licking Bush's fingers and thinking you're free" is not going to win many people over to your side.
While there are many theories as to the best way to get political power, I subscribe to the one that says you select the party which is most similar to your beliefs and work from there.