I read in an old article (
https://www.theguardian.com/world/2004/oct/22/uselections2004.usa) that Nader's 2004 voters looked a lot like Perot's 1996 voters--"economically populist, anti-corporate, blue collar ... much more conservative than Nader 2000." There's a decent chance some voted Buchanan in 2000, especially considering these people don't mind breaking for an independent/third party anyway.
Also Pat Choate, economist and Perot's 1996 VP, did just this. (
https://web.archive.org/web/20060516135930/http://www.commondreams.org/headlines04/0309-11.htm)
