Why was there a third-party surge in 1992?

[SingingAnalyst]

I think Perot appealed to people who supported Pat Buchanan and felt that Clinton and HW were equally compicit in the "giant sucking sound".

This, plus the fact that Clinton was not trusted (the April 20, 1992 Time Magazine cover admits as much, and was used in a Bush ad). Bush was very unpopular and was seen as a "do-nothing" President in the face of a recession (though his popularity had reached the high 80s early in 1991 during the Gulf War).

Plus, Congress was seen as part of the problem, and a leader who could "shake up Washington" was sought after. Many remarks were made to the effect that 99% of Congress was re-elected in 1988, and that the same party had controlled the House for 38 years; term limits were popular (a term limit proposal passed in MI in 1992).

Clinton's lack of perceived trustworthiness dogged him well into his first term, and was a factor in the 1994 GOP takeover of Congress; Clinton's poll numbers were low (by pre-Trump standards) until the April 1995 Oklahoma City bombing, whereupon they jumped several points and kept rising.

[SingingAnalyst]

People today forget just how much Americans didn't trust the Democrats to hold the presidency again circa 1992.  The Dems had lost three straight elections, and states like New Jersey and California still voted Republican because the voters in those states assumed that Democrats would raise their taxes and destroy the economy if elected.  In one of the Naked Gun movies, Leslie Nielsen's character quipped, "Why can't the Democrats put up anyone worth voting for?"  It was an inside joke demonstrating that LA/NYC liberals wanted a Democratic president but that they thought the Democratic Party was floundering at actually being able to put together a solid presidential campaign.

But at the same time, the country was blaming Reagan/Bush for the recession and the deficit, and Baker/Dole establishment Republicanism didn't seem like the answer either.  So when Perot rode in with "centrist populism," it gave Americans a third way that seemed somewhat interesting, without having to choose between stale Reaganism, boring Dole-ism, or radical Dukakis-ism.

When Perot flamed out, Clinton was able to sell a sort of suburban-friendly version of liberalism as the new third way, and win the election.  Not sure if another Democrat would have been able to do the same.  Clinton was the ideal sort of opportunist to somehow manage to piggyback on Perot's voters to a win.

I consider Bill Clinton to be perhaps the most politically gifted American politician of my lifetime, not even merely my living memory.

On a 1992 episode of the Tonight Show, at the time of Perot's maximum popularity (before Perot temporarily dropped out), Jay Leno (who had just replaced retiring Johnny Carson) pointed out that, if the election were held that day, Clinton would only carry his home state of Arkansas. He then quipped "Clinton appears to be a typical Democrat after all."