The two major-party candidates that are almost certain to contend in this year’s election are the most despised in at least a quarter-century. For that reason alone, you might think a third choice would emerge, but you would be wrong. The reason has nothing to do with America’s voters.

But first, it’s important to understand how negatively voters view the candidates.

In mid-April, a Wall Street Journal/NBC News poll found that just 32 percent of registered voters in both parties viewed Hillary Clinton favorably, and 56 percent viewed her unfavorably, for a net negative margin of 24 percentage points. For Donald Trump, the negative margin was considerably worse: 41 points (24 percent favorable, 65 percent unfavorable).

The net unfavorables of each were the highest recorded in the past 24 years – by a mile. A Wall Street Journal analysis on Friday found that only two of the previous 12 nominees of the two major parties had net unfavorables of any sort at this point in April of election year: Bill Clinton in 1992 at minus-11 and Mitt Romney in 2012 at minus-5.

Of course, the Trump and Clinton figures can improve. Or can they?

The Journal’s polling data show that only two candidates managed to boost their their net more than five points between April and just before the November election: Bill Clinton in 1992, up 18 points, and Barack Obama in 2008, up 14 points. In both cases, the candidates were relatively unknown in April: one a governor of a small state, the other a first-term Senator. By contrast, Hillary Clinton and Trump are very well known. Even if each candidate improves as much as Bill Clinton did, the net for Hillary Clinton would still be the highest in history on an election eve; Trump’s net would be minus-23 percent, astronomically higher than the previous record.

In fact, only one candidate since 1992 has gone into the election with negative favorability. That was George H.W. Bush in 1992, at minus-5. Judging from history, we can confidently predict that both the candidates will go into this election with negatives in double digits, possibly in the twenties or thirties.

In a survey released Friday, the New York Times/CBS News poll, confirmed the WSJ/NBC findings, though its net unfavorable were not quite as glaring. Trump was viewed favorably by just 26 percent of registered voters and unfavorably by 55 percent; Clinton’s scores were 31 percent favorable, 52 percent unfavorable.

The NYT/CBS poll also asked, “Does the candidate share your values?” For Trump, only 31 percent of respondents said yes; for Clinton, 37 percent. Asked if the “candidate honest and trustworthy,” just 31 percent said yes for Trump, 32 percent for Clinton. On whether the candidate has “the right kind of temperament,” 27 percent answered affirmatively for Trump, 48 percent for Clinton.

These abysmal results reflect an electorate crying out for a third choice.

A new Fox News poll found that Gary Johnson, the former New Mexico governor who is the likely Libertarian Party nominee for president, was the choice of 10 percent of registered voters in a three-way race with Clinton and Trump. That’s a surprisingly strong result because most people have no idea who Gary Johnson is. What all the respondents know for certain is that he is not Clinton or Trump.

Johnson, who announced this week that former Massachusetts Gov. William Weld, a Republican, will be his vice presidential running mate if he’s nominated, has an advantage over any potential independent in 2016: his party is on the ballot in all 50 states. Other candidates would have to gather signatures to qualify, and time is extremely short.

The real question, however, is why – at a time when independents outnumber both Democrats and Republicans by wide margins – an independent candidate did not step up earlier. The answer is pretty simple. The two parties have stacked the deck. Independents and third-party candidates have to gather millions of signatures, they are drastically limited in the amounts they can raise from donors, and, worst of all, they face a practically insurmountable obstacle in the rules for admission to the final fall presidential debates. And if you aren’t in the debates, you can’t get elected president.

As Pat Caddell, the veteran Democratic pollster, wrote this week in The Hill: “The Democratic and Republican parties, with full malice and intent, have acted to create a rigged duopoly. Neither wants a third challenger, and both have actively colluded to prevent one from ever having a chance.”

It’s highly unlikely that any candidate, including Gary Johnson, can meet the 15 percent threshold for access in five polls taken shortly before the first debate in September. No candidate who hasn’t participated in the Democratic or Republican primaries has achieved their level in the past half-century. Ross Perot was polling at just 8 percent before he was admitted to the debates in 1992. After he ended up with 19 percent of the vote in the actual election, the Commission on Presidential Debates (CPD) changed the rules. No more Ross Perots.

The CPD is the great unrecognized villain in the story of why Americans don’t have a chance to vote for an independent candidate. Caddell calls this private, secretive organization – headed by the former chairman of the Republican National Committee and the former press secretary to Bill Clinton – “the worst blight on our democracy.”

Americans are crying out for a third choice. Six out of seven voters say the political system is badly broken. By a margin of two to one, they want a third person on the stage for the presidential debates. But, unless the courts rule otherwise, that’s not going to happen in 2016 – a year when, by a landslide, Americans reject both candidates of a duopoly bereft of support and legitimacy.

Ambassador Glassman served as Under Secretary of State for Public Diplomacy and Public Affairs in the George W. Bush administration. He is one of 49 political, academic, business, and military leaders who signed a letter demanding the Commission on Presidential Debates change its rules to permit an independent to debate.