One big problem is that Perot and then Buscanan´s Reform Party was nothing more than a personality cult. He would have trouble creating a real politcal party.
And that is part of the reason why third parties have so much trouble. In my mind, there are five reasons why this is so. Allow me to list them.
1. Voting, debate, and ballot access laws. The two major parties have made it very difficult for third parties to obtain ballot access and to make it into the debates, and the Electoral College doesn't make things any easier.
2. Cults of personality. Paul V McNutt put it perfectly. Many third-party runs - Ross Perot in '92 and '96, Ralph Nader in 2000, Teddy Roosevelt in 1912 - are built around the strength, charisma, and message of the candidate, not their party. These parties may have one great year, winning double-digit vote percentages and even a couple of states, but when that figure leaves the party, it collapses by the next election. The fall of the Reform Party in the late 1990s is a textbook example of just such a collapse.
3. Fringe ideologies. Eugene Debs' Socialist Party of the early 20th century is a prime example of this. They couldn't moderate their socialist ideology and bring it from the inner-city to Main Street, which meant that they had a lot of trouble getting more than five percent of the vote. Today, the three largest third parties - the Greens (leftist and environmentalist), the Libertarians (obsessed with individual freedom, at any cost) and the Constitution Party (protectionist and Christian fundamentalist) - all have this problem, even though their solid ideologies tend to make them very durable.
4. Single issues. Parties built around single issues tend to fade away once their positions on those issues become unpopular, or when one of the major parties co-opts their position. For example, take the American Independent Party. In 1968, both parties were supporting civil rights, which caused the diehard white supremacists to defect and support a third party. Enter George Wallace and the AIP, which took up the banner of segregation and won five states in the Deep South. By 1972, racism was becoming increasingly unpopular, leading to the failure of the AIP to win a single state.
5. Disenchantment with both major parties. Protest candidates and parties are usually the only ones that see any success in elections, and it often ties into the personality cults. Leftists voted for Nader in 2000 because they felt that both Bush and Gore were the candidates of big business. Many people voted for Perot in 1992 and 1996 because they felt that neither party could run the country. Moderates voted for Anderson in 1980 because they were upset with Carter's failed policies, but they felt that Reagan was too conservative. And this year, you'll probably be seeing social conservatives (less so after Palin) and the Ron Paul crowd voting for Bob Barr.