His base was:
- Those who think 'America should be run like a business'. Lots of Americans think this even after W and Trump.
- Those who mouth the 'Ds are too far left, Rs are too far right' mantra. Perot fit this, campaigning to the left on social issues and the right on economic issues.
- Those who wanted an outsider. Bush was perceived as a failure due to the recession and jobless recovery, while Clinton was "slick Willie".
- NAFTA (that giant sucking sound), as others have stated
- Deficits. He didnt propose any real solutions to the Reagan deficits but he at least paid lip service to deficit reduction, while Bush had no credibility on it as the incumbent and voters never consider Ds as deficit cutters.
Clinton was running 3rd and there was even some chatter of Ds losing major party status in future elections for a good chunk of the time before Perot pulled out. But Perot never really regained his status when he got back in.
It would be interesting to see the correlation between Perot and Trump voters.