Washington (CNN) Gary Johnson is the new punching bag of the 2016 campaign.

The Libertarian presidential candidate is the subject of intensifying ridicule following his latest televised flub when he couldn't name a world leader he admired during a Wednesday interview with MSNBC's Chris Matthews. That follows another embarrassing on-air moment last month when, in response to a question about how he would alleviate the plight of the besieged Syrian city of Aleppo, he responded: "What is Aleppo?"

The gaffes, combined with his failure to make the debate stage and his infinitesimal chance of winning the White House, raise a pressing question: Why is Johnson still in the race?

Democratic nominee Hillary Clinton ribbed Johnson Thursday by pretending to struggle when she was asked to name a world leader she admired. But she made clear her view that she and her Republican counterpart, Donald Trump, are the only viable candidates.

"Either Donald Trump or I will be the President of the United States," she told reporters on her campaign plane, sending a clear warning to disaffected Democrats flirting with Johnson. "People have to look carefully in making their decision. It will be either him or me."

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But Johnson isn't going anywhere.

William Weld, Johnson's running mate, said the latest stumble doesn't leave him with any doubts.

"He's a deep person in terms of his thinking and he thinks through things in a way that many other people don't," Weld told CNN's Randi Kaye Thursday on Anderson Cooper 360. "Pop quizzes on television are obviously not his forte but depth of analysis and surprising lines of analysis are his forte. I think he just needs time to expound what he's thinking."

Johnson's decision to stay in the race isn't just an academic question. He and Weld are doing well enough in swing states to pull votes from both Trump and Clinton. In the latest CNN/ORC poll of Colorado — a state Clinton must win and which her campaign thought was already safe — Johnson is polling at 13% among likely voters while Clinton trails Trump 42% to 41%.

Market for Johnson

Third party candidates have traditionally had a rough ride in the two-party US election system — none have made a significant national impact since billionaire Ross Perot grabbed 19% of the vote in 1992.

But amid the most polarizing election in years featuring two major party nominees with historic unfavorability ratings, there may be a market for Johnson's character and ideas.

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"Something is obviously different this time," said Kyle Saunders, a political analyst at Colorado State University. "Part of it is the unpopularity of the two major party candidates. The strongest of partisans are behaving the way they always behave."

He added: "Those other people who are not the strongest partisans are looking for some other places to cast their ballot."

And the more that the chattering classes disdain Johnson, the more stubborn he seems to get.

"It's been almost 24 hours ... and I still can't come up with a foreign leader I look up to," Johnson tweeted defiantly Thursday.

'Gotcha-ism at its worst'

Johnson's campaign manager, Ron Nielson, blasted Johnson's critics as being guilty of "gotcha-ism at its worst" in a Facebook post and said that the oversight just proved that his candidate was just like other Americans.

"Gary Johnson is a real person. A pragmatist and the kind of leader that people can respect and trust," Nielson wrote. "Unfortunately, as most Americans have come to realize, this is not the case with Clinton and Trump."

It was not the first time that a presidential candidate has stumbled in a world leader pop quiz that raised doubts about their credentials to be President. In 1999, then-GOP frontrunner George W. Bush was stumped when asked by a Boston reporter to name the leaders of Chechnya, Taiwan, India and Pakistan.

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And gaffes don't seem to derail a candidate in 2016 the way they once did.

After all, Trump has made statements that are far more outrageous than Johnson's comments -- on an almost daily basis -- and he is locked in a tight race with Clinton.

It's debatable whether true Libertarian voters — those who support the party because it favors a disentangling from foreign quagmires and a less robust US global role — are that bothered that their candidate is not deeply acquainted with the details of the Syrian civil war.

Pressure on Johnson

But it's not just verbal stumbles that are beginning to build pressure on Johnson.

His political position is also eroding because of his failure to hit the 15% polling threshold needed to muscle his way into the debates between Clinton and Trump.

Back in June, Johnson told The New Yorker that if he missed what he called the political "Super Bowl" — "There's no way to win."

There are reasons -- beyond the disdain that a large proportion of the electorate appears to hold for Clinton and Trump -- for Johnson to stay in the race.

First, he appears to have the chance to make tangible progress for the Libertarian Party across the nation. In 2012, Johnson ran for President and won just under 1% of the electoral vote. Even if he only cracks 5% this time, that would represent an undeniable step forward for the party.

But there's a more fundamental reason why Johnson may resist calls to quit.

He explained in an op-ed piece in the New York Times on Wednesday that the American political system, by producing such alienating rivals as Clinton and Trump, has failed. That, he argued, means reformers have no choice but to fight.

"Hyper-partisanship may be entertaining, but it's a terrible way to try to run a country. We're the alternative — and we're the only ticket that offers Americans a chance to find common ground," Johnson wrote.

Johnson also appears to be building a significant base of support among millennial voters -- a demographic that Clinton needs to dominate to make it to the White House -- but which could fuel Libertarian Party growth in future.

A Bloomberg News/Selzer & Co. poll released Monday found Clinton's 10-point advantage among younger voters cut to a statistically insignificant four points when Johnson and Stein are included in the race.

While some Democrats who abhor Clinton might be tempted by a fling with Johnson, he is also providing a refuge with Republicans who cannot stomach Trump. Antipathy for the billionaire prompted the Detroit News Thursday to do something it has never done in its 143 year history -- endorse someone other than the Republican presidential candidate.

Concern for Democrats

Still, Johnson's resilience is causing genuine concern for top Democrats.

"There's one message I want to deliver to everybody: If you don't vote, that's a vote for Trump. If you vote for a third-party candidate who's got no chance to win, that's a vote for Trump," President Barack Obama said on the Steve Harvey radio show this week.

Vice presidential nominee Tim Kaine is warning wavering Democrats attracted to Johnson that they risk bringing about an electoral catastrophe similar to the one in Florida in 2000 when Ralph Nader siphoned votes away from Vice President Al Gore. That allowed Bush to claim Florida after the vote count showdown in the US Supreme Court.

"If Gore had been president, we probably wouldn't had a war in Iraq," Kaine told Yahoo News' Katie Couric last week. "Casting a vote, a protest vote, for a third-party candidate that's going to lose may well affect the outcome. It may well lead to a consequence that is deeply, deeply troubling. That's not a speculation, we've seen it in our country's history."