Perot was an obvious nutcase, ran awful campaigns, and still pulled a fifth of the electorate, on an incoherent populist platform.
We have, as a nation, some critical problems to solve - illegal immigration, massive wealth redistribution, denial of almost all the rights enumerated in the Bill of Rights, and government spending, just to name some big ones - where there is no path to a solution through either major party.
A third party that is not crazy like the LP, and not a single-issue party, and not based on a single personality, has a lot of room to work with.
By definition, third parties are made up of fringers who are unhappy with the two major parties.
What do they want? Single issues, a cult of personality, or, like the Constitution Party, take a position (oppose the war on terror) that is crazy.
Third parties don't work, and never have.