The Commission on Presidential Debates announced Friday that the Libertarian nominee Gary Johnson failed to qualify for the first debate on Sept. 26 because his polling numbers were below the 15-percent threshold. According to the five polls used by the commission, Johnson averaged 8.4 percent support.

What this means is that Johnson becomes the most popular presidential contender in modern history not to have his own lectern on the debate stage.

On Wednesday, Johnson had purchased a full-page advertisement in The New York Times to plead his long-shot case to the commission. The Libertarian candidate argued, “The conditions of the presidential election of 2016 are extraordinary and without precedent. The collective destinies of millions of voters now come down to the methodologies of pollsters … [and] your organization.”

That same day, Quinnipiac University released a poll (not used by the commission) giving Johnson 13 percent of the vote, his highest total in any national survey. That poll found that Johnson was running neck-and-neck with Hillary Clinton for first place among voters below 35 with Donald Trump third.

It is possible that Quinnipiac was overstating Johnson’s support. But even based on these debate commission averages, Johnson is polling higher than the mid-September 1996 numbers for Ross Perot (about 7 percent) which led to his absence from the debate stage on his second try for the White House.

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No similar claim for credibility can be made for Green Party nominee Jill Stein — who has never held public office, recently went to the wrong city for a rally, faces a warrant for her arrest from a recent protest in North Dakota, and is averaging less than 3 percent in the polls.

Admittedly Johnson, the marijuana-using, former two-term Republican governor of New Mexico, has had his stumbles. During a recent TV interview, he failed to recognize the name of the beleaguered Syrian city of Aleppo. But with his running mate, former GOP Massachusetts Gov. Bill Weld, Johnson has put together a Libertarian ticket that exceeds the minimal standard for seriousness.

The 15-percent polling requirement is an arbitrary artifact of history. It was originally developed by the League of Women Voters, the prior sponsor of the presidential debates, to deal with the dilemma presented by the 1980 independent candidacy of liberal Republican Illinois congressman John Anderson.

Once a novelty

Presidential debates were still a novelty in 1980. The two major party nominees had faced off only twice (1960 and 1976) in the prior five elections. President Jimmy Carter, fearing that Anderson would cost him votes, boycotted the first debate between the independent candidate and Ronald Reagan. Only in late October, with Anderson on the sidelines because of dwindling poll numbers, did Carter and Reagan hold a single debate.

The bipartisan Commission on Presidential Debates retained the 15-percent standard when it replaced the League of Women Voters prior to the 1988 election. Four years later — with Perot polling in the high teens in the run-up to the mid-October debates — it was inevitable that 1992 would be remembered as the year of three dueling lecterns.

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Vice Admiral James Stockdale, Perot’s reluctant running mate, also made history with his wobbly opening lines in the vice presidential debate: “Who am I? Why am I here?”

Stockdale, who had won the Medal of Honor for his bravery during seven years as a Vietnam POW, was viciously portrayed as a senile old man afterward. The unfairness of that media characterization is a reminder of the cruelty of presidential politics.

Perot was considered to have held his own in the three debates with Arkansas Gov. Bill Clinton and President George H.W. Bush. A Harris Poll, after the 1992 debates, found that 43 percent of the voters believed that Clinton was most effective, 33 percent were persuaded by Perot and only 18 percent said Bush had impressed them.

The Anderson and Perot precedents can work both ways. They illustrate that debate sponsors have never bent the rules on polling in the past. But they also illustrate that having an independent candidate on stage in a presidential debate does not undermine the gravity of the occasion.

Not a normal election

In a normal election, it might be tempting to propose that Johnson should be added to at least one of the later debates, even if he continues to poll under 15 percent.  But as the Libertarian nominee himself admitted in his newspaper ad, this is an “extraordinary” election “without precedent.”

Never have debates been so important to bring home to the voters the stakes in an election. The new orthodoxy this week is that Donald Trump — a mendacious real estate hustler who seemingly has never read a book and lacks any grasp of the world — could be elected as the 45th president.

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A clotted Republican presidential field meant that Trump was rarely directly challenged on his march to the GOP nomination. Never did any Republican have the luxury of squaring off with Trump on a debate stage without other candidates getting in the way. As a result, Trump was able to mug his way through the debates without facing the political consequences for his vicious attacks and willful ignorance.

Hillary Clinton, for all her flaws and failings, is the only person standing between Trump and the Oval Office. Cluttering up the debate stage with a third candidate — whose presence will inevitably change the tenor of the evening — is far too risky. It’s dangerous enough that America is currently chancing handing the nuclear codes to a bilious billionaire.

Roll Call columnist Walter Shapiro is a veteran of Politics Daily, USA Today, Time, Newsweek and the Washington Post. His book on his con-man great-uncle was just published: “Hustling Hitler: The Jewish Vaudevillian Who Fooled the Fuhrer.” Follow him on Twitter @MrWalterShapiro.