Two obscure southern governors - Jimmy Carter and Bill Clinton - defeated sitting presidents - Gerald Ford and George Bush snr - respectively. When Carter ran for re-election, he was thrashed by ex-movie star Ronald Reagan, in some respects the Trump of his day in that he was also dismissed as too simplistic in his analysis and prescriptions to be president.
George Bush jnr, another southern governor, defeated Vice-President Al Gore and African-American neophyte Obama defeated Senate institution John McCain. When sitting presidents were re-elected - Reagan in 1984, Clinton in 1996 and Obama in 2012 - their opponents were establishment figures, respectively former Vice-President Walter Mondale, Senator John Kerry and Mitt Romney, the epitome of big business Republicanism.
But on reflection, I didn't go far enough: Trump isn't just an outsider; he is, in the context of presidential politics, an outlaw.
All 17 Republican candidates knew the hot-button issue on the right was immigration but only Trump addressed it in the visceral terms their constituency wanted to hear. His extreme rhetoric - Mexican immigrants are rapists - and solution - build a wall and make Mexico pay for it - gave him ownership of the issue and showed he's not just another politician trotting out talking points.
Many pundits viewed his blistering attacks on George W. Bush and the Iraq war as damagingly disloyal and a strategic blunder. In fact by denouncing a war that everyone who's not a card-carrying neo-conservative knows deep down was disastrously counter-productive, Trump sent a clear message that he's uncompromised by any sense of obligation to an unloved party hierarchy.
Jeb Bush, who staggered through the campaign handicapped by his brother's tainted legacy and the establishment's seal of approval, insisted until the bitter end that W had "kept America safe". Only his family was listening.
Trump's vulgarity and the undercurrent of violence in his rhetoric - this week he declared he wanted to punch a protester in the face - locate him in popular culture rather than politics.
American popular culture is full of outlaw figures whose appeal derives from their ability to get things done via decisive, often violent, action while the system pussyfoots around. One thinks of The Godfather's opening: seeking revenge on the men who beat his daughter, the undertaker Bonasera goes to Don Corleone who chides him for thinking he could get justice through courts.
Trump's brutal flippancy - challenged over his characterisation of various women as "fat pigs, dogs, slobs and disgusting animals", he smirkingly responded "only Rosie O'Donnell" - brings to mind another Mafioso, the monstrous yet mesmerising Tony Soprano.
Or how about Clint Eastwood's Harry Callahan, the archetype rogue cop? In Dirty Harry, the implacable cop sets out to end an extortionist's reign of terror by any means necessary and in wilful defiance of the constraints imposed by a politically correct system more concerned with the rights of perpetrators than those of their victims.
When innocent lives are at stake, Harry doesn't resile from torture. Trump has vowed to bring back waterboarding and "a hell of a lot worse" because that's all terrorists deserve.
The celebrated movie critic Pauline Kael described Dirty Harry as "a right-wing fantasy that propagandises for para-legal police power and vigilante justice" and a "remarkably single-minded attack on liberal values". She could have been describing Trump's candidacy.
But unlike the Don, the Donald isn't a fictional character. He's real and he's running for president.
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