Hillary Clinton lampoons gaffe-prone Libertarian Gary Johnson but privately frets he could cost her White House

Democrats blamed Ralph Nader for giving Florida – and the White House – to Bush in 2000

Hillary Clinton has been lampooning Libertarian Gary Johnson and his stumbles in interviews but her jokes mask a deeper anxiety that votes for him could deny her the keys to the White House.

However egregious Mr Johnson’s lapses may appear to some Democrats – this week he was unable in an MSNBC interview to name a single foreign leader he admired – he is still drawing roughly 8 per cent support nationally. In some key swing states, he is doing better than that.

On her way to a Chicago fundraiser, Ms Clinton was asked by reporters if she had a favourite world leader and she evinced a moment of confusion, by way of poking fun at Mr Johnson. “Oh, let me think,” she replied sarcastically, before going on to name Angela Merkel of Germany.

She chose to skirt the more serious question about whether the continuing presence of Mr Johnson, a former Republican Governor of New Mexico, in the presidential contest worried her. She did, however, send a message to Democrats flirting with giving him their vote.

“Either Donald Trump or I will be the president of the United States, and so people have to look carefully in making their decision about who to vote for, because it will either be him or me and I am going to do everything I can to make sure it’s me,“ she said.

Mr Johnson has twice humiliated himself on national television of late. Earlier this month when he was asked what he would do as president about the tragedy in Aleppo, Syria, he replied, “What is Aleppo?” He later apologised for the astonishing display of ignorance, but since has become a punchbag on the late-night talk shows.

The history of third-party candidates trying to break the mould of America’s two-party system is not a happy one. The last to make any serious inroads was Ross Perot who achieved 19 per cent of the vote nationally in 1992 when Bill Clinton beat incumbent George H W Bush.

Yet Mr Johnson, whose running mate is William Weld, a former Republican Governor of Massachusetts, continues to have traction, in part because both of the mainstream candidates this year suffer from historically poor popularity ratings, something he highlighted in an opinion column in the New York Times this week.

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

While Mr Johnson would surely take votes away from both Ms Clinton and Mr Trump, there is concern among Democrats that it is their candidate who might suffer the most. He is drawing strong support from millennials, for instance, some of whom supported Bernie Sanders for the Democratic nomination and are still not willing to shift their support to her.

A Bloomberg News/Selzer & Co poll this week found Ms Clinton’s 10-point advantage among younger voters cut to a statistically insignificant four points when Johnson as well as Jill Stein, the Green Party candidate who is drawing about 1 per cent nationally, are included in the race.

History also has its warnings. In 2000, it was Ralph Nader’s Green candidacy that ended up syphoning enough votes away from Al Gore to help tip Florida by the slimmest of margins to George W Bush, a hotly contested result that eventually delivered the White House to him.

Gary Johnson at a ‘Reason’ magazine photoshoot in 2012 (Gage Skidmore/Flickr)

“If Gore had been president, we probably wouldn’t had a war in Iraq,” Tim Kaine, Ms Clinton’s running mate told Yahoo News 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.”

President Barack Obama has also been sending out warning signals about the apparent lure of Mr Johnson to some voters who would otherwise back Ms Clinton. “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,“ he said in a radio interview.

Not helping are the few major newspapers which, while they have ended decades-long traditions of backing Republicans because of their distaste for Mr Trump, have plumped for Mr Johnson, not Ms Clinton. That was the stance most recently of the Detroit News, the biggest paper in the biggest city in Michigan, a crucial state for the Democrat.

“We recognise the Libertarian candidate is the longest of long shots with an electorate that has been conditioned to believe only Republicans and Democrats can win major offices,” the newspaper’s editorial board wrote on Thursday. “But this is an endorsement of conscience, reflecting our confidence that Johnson would be a competent and capable president and an honorable one.” New Hampshire’s Union Leader also endorsed Mr Johnson.

Mr Weld moved to defend Mr Johnson after his latest gaffe. “He’s a deep person in terms of his thinking and he thinks through things in a way that many other people don't,” he told CNN. “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.”