So many things about this election are unprecedented — and one of the most obvious is how much voters dislike the candidates. By now, everyone knows that this year features the two most unpopular presumptive major-party candidates on record.

But in some ways, Americans' dislike of the presidential candidates isn't so remarkable. In fact, a recent report from the Pew Research Center shows that 1992 voters were just as disappointed in their candidate choices, perhaps even more so, than voters are today. That helped open the door to the most successful third-party candidate (by popular vote) in more than 100 years, Ross Perot.

This year, despite constant chatter about independent candidates and new interest in the Libertarian and Green parties, no outsider candidate has looked competitive yet (though some polls have shown Libertarian Gary Johnson polling in double-digits). Perot's 1992 run is an excellent foil for showing what is making a third-party run particularly difficult this year.

The political landscape in 1992

In June 1992, only around 40 percent of Republicans or Republican leaners were "very" or "fairly" satisfied with their choices: sitting Republican President George H.W. Bush, Arkansas Gov. Bill Clinton and businessman Perot, running as an independent.

So what were people so upset about? This 1992 article from the New York Times spells it out: 78 percent of Americans disapproved of Bush's handling of the economy.

Indeed, the U.S. was just out of a recession, with unemployment peaking at 7.8 percent in June 1992. And even a quote from a 1992 Bush adviser would fit perfectly into many articles about this year's election: "It's clear that no matter what the economic statistics show, voters still do not feel the economy is getting better."

Meanwhile, Clinton was dogged by accusations that he had avoided the draft in 1969, as well as reports of extramarital affairs.

1992 voters' specific grievances with the candidates were different from those of 2016 voters, but a couple of other statistics make 1992 look a lot like 2016. Both major-party candidates had upside-down favorability ratings: By one poll, Bush, at the end of June, had a net favorability of -15, and Clinton was at -24.

Americans were also pessimistic in general about the state of politics: Their trust of Washington was low and getting lower — 29 percent of Americans in July 1992 said they trust government "just about always" or "most of the time." As of 2015, that figure was at 19 percent.

In the aftermath of the election, voter dissatisfaction for the other two candidates was understood to have opened the door for Perot, who would, come November, earn nearly 19 percent of the popular vote (but win no states).

What did Perot have that Gary Johnson doesn't? (Aside from charts)

This year, third-party candidates are doing well, at least compared with the last presidential election — the media have certainly started paying more attention this year.

Recent three-way matchups between Johnson, Trump and Clinton show Johnson with anywhere from 4 percent to 10 percent support. Four-way polling matchups including the Green Party's Jill Stein show that, combined, Johnson and Stein have the support of anywhere from 7 to 14 percent of registered voters.

That's respectable compared with 2012, when Johnson and Stein were also the respective Libertarian and Green nominees. On Election Day, Johnson came in with about 1 percent of the vote in 2012, and Stein with less than half a percent.

But that's nothing compared with 1992. At one point early that summer, Perot led Bush and Clinton, with the support of 39 percent of voters, and he eventually went on to get 19 percent of the vote.

What was on Perot's side? Dissatisfaction with Clinton and Bush helped him gain a foothold — particularly dissatisfaction with the economy under Bush — but a few other things boosted him:

1. Money: The most obvious factor: Perot was able to self-fund, dumping an estimated $68.4 million into his campaign (more than $117 million, in today's dollars). That helped him drive that campaign's ad spending upward (and it gave America Perot's memorable prime-time "infomercials").

2. An open lane: Another thing that boosted Perot was that Bush and Clinton were both viewed as somewhat centrist, according to James McCann, a professor of political science at Purdue who has studied third-party candidates. Bush had reneged on his famous "no new taxes" promise, upsetting conservatives. Clinton, meanwhile, was a "new Democrat," running as a centrist.

That left Perot plenty of room. "There's also this argument out there in the literature that when the two major nominees sort of converge in terms of issues, they leave open a space that somebody else can fill," McCann said. "When that happens, that can encourage third parties and give them sort of traction."

While neither Hillary Clinton nor Trump are at the ideological extremes of their parties, they are certainly far apart on most issues. A centrist candidate may have been able to appeal to moderate voters, but one hasn't shown up (and by now, it's already too late to get onto the ballot in some states). And in some ways, Trump occupies the Perot space this year (appealing to white voters, railing against trade and promoting isolation), as David Bernstein wrote in Politico Magazine.

Johnson and Stein, of course, have nearly four months to gain more ground, but McCann points out that an independent candidate would have more freedom to maneuver to somewhere between Clinton and Trump.

"[Johnson] is a libertarian. He can't diverge much from his own party's orthodoxy," he said. "If you were going to find a genuine third-party candidate who would be competitive, you'd say, 'OK, what are the issue gaps here?' "

Plus, while people say they want an independent kind of candidate, it's exceedingly hard to find ideological agreement among those disaffected voters.

Other Pew findings go hand in hand with this idea of Trump and Clinton being so different: For example, 74 percent of voters say it "really matters who wins" the election, the highest measure since 2000.

Pew also finds that the majority of Trump supporters (55 percent) are voting against Clinton. And about equal shares of Clinton supporters are voting against Trump (50 percent), versus 48 percent voting for her, according to Pew's data.

Pew doesn't have data on this question from this point in 1992, but as of that October, 57 percent of both Clinton and Bush's respective voters said they were voting for their candidates. (Then again, at that point, voters were more satisfied with their candidates.)

3. Lack of polarization: American voters simply weren't as polarized in 1992 as they are today. The fact that this year's voters are so opposed to the other party squares with recent findings about growing political polarization. Pew has found that in the past two decades, Democrats and Republicans have grown farther and farther apart ideologically. Affective polarization — simply put, how much liberals and conservatives dislike each other — is on the rise as well.

One astounding measure of this: As of 1960, only 4 percent of Democrats and 5 percent of Republicans said they would be "displeased" if their son or daughter married someone of the opposite party, according to a 2012 study from Stanford University. In 2010, the shares who would be "somewhat or very unhappy" were 33 percent for Democrats and 49 percent for Republicans.

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