When Ed Miliband was elected Leader of the Opposition in 2010 it came as a complete shock.
While David Miliband was touting himself as Tony Blair's natural successor, Ed worked behind the scenes to court union support. On one hand this was an impressive strategic manoeuvre, but on the other he had just stabbed his own brother in the back.
Perception is everything in politics. This fraught relationship between the brothers stuck with him, as did a disastrous cocktail of fantasies about his party.
His lot had wrecked the nation's finances, opened the borders, decimated the Middle East, gone soft on the bankers, ramped up the welfare bill, gave away Britain's sovereignty, and pumped society full of political correctness.
After the 2010 election the Labour Left was too withdrawn - embarrassed by the pro-market position of the Blair administration - to fight back, while the Labour Right was too cocksure to notice this narrative was beginning to take shape.
Meanwhile, the Conservatives remained at work. They were adamant a Miliband government would not only toy with the nation's defences, but spend its way into another recession, go easy on welfare scroungers, and concede everything to the over-pampered Scottish nationalists.
The truth didn't matter. Once these ideas had been accepted by the public, that was it for Labour. Being "too left wing" - as the British Election Study 2015 suggests - is a red herring. The only man with the skill to counter such an aggressive narrative was Tony Blair.
But Blair is gone, and so are the Milibands. So is Burnham (to an extent). So is Cooper. So too, on the face of it, is almost every major figure linked with the last 20 years of Labour's history: Blair's babes, the Brownites, Miliband's inner circle - the lot of them have banished themselves into retirement, or the backbenches.
Perhaps this is why the Conservatives remain weary. The arsenal of weapons Osborne and Cameron have built over the last decade to bash the Labour Party may not be so effective moving forwards.
Cameron can no longer score points by blaming the problems of today on the "ruinous policies of the last Labour Government" - Corbyn has rebelled against his own party over 500 times since 1997, and openly resents Tony Blair's politics.
Unlike Miliband and Balls, who were so deeply embedded in the Treasury they formed part of the fixtures when Gordon Brown "crashed the car", Corbyn and McDonnell were, to borrow a phrase, so far backbench they'd fallen off.
Neither can the Prime Minister throw 'Mid Staffs' and 'PFI' over the dispatch box, huffing and puffing his opposition counterpart had the audacity to "weaponise" the NHS. Jezza, for the most part, agrees with Dave.
There are charges, however, that will stick. The economy will be the main weakness for any Labour leader until the end of time itself given the Tories avoid another moment like the Exchange Rate Mechanism withdrawal in 1992.
Welfare spending and immigration, unless the Conservatives fail (again) to live up to their manifesto commitments, will forever "spiral out of control" under a Labour government.
But what about the man? Although Red Ed was anchored by his "bruising" family relationship and weighty political baggage, Corbyn is an unknown quantity as far as regular voters are concerned.
That being said the new Labour leader must move fast to fill in the blanks - and on his own terms - as his enemies are already at work.
In the space of one week he has been painted as a sexist, scruffy, anti-semitic, adulterous, IRA-sympathising 1980s throwback who hates Queen and country, and wants to disband the armed forces. Did I mention he's an Islamic State apologist?
I don't know whether this narrative will stick. And if it does, it will take some time. His team, meanwhile, have a wealth of material from which they can weave a story of their own:
Most people, including his opponents, see him as a man of principle; he says what he thinks and he does what he says. He is also a man of integrity; in the aftermath of the MPs expenses scandal he emerged he the country's lowest expense claimant.
Refreshingly, the new Labour leader does not 'do spin' like his predecessors, no matter how many spin doctors and special advisers he hires in future to perpetuate this idea.
He is the true 'change candidate'. David Cameron said he wanted to change PMQs when he became party leader ten years ago. Ed Miliband said he wanted to change PMQs when he became party leader five years ago. Jeremy Corbyn did it three days into his leadership.
Although his first week was littered with childish mistakes, it shows that he's just one of us and not a machine politician. Neither is he a shameless Labourite careerist climbing the greasy pole for a shot at power, despite having served as a member of parliament for over 30 years.
Jeremy Corbyn is, above all, a man who has continuously beat the odds. He scraped himself onto the leadership ballot with two minutes to spare when the consensus said he would fail. The 200-1 candidate won the contest with a staggering 59.5% of the vote share when the consensus said he would finish last. He put together a shadow cabinet from all wings of the party when the consensus said factions within the PLP (Parliamentary Labour Party) would revolt, bring him down, or defect.
The consensus now says he will only last a few months. Presented with such a low bar, his team won't find it difficult to generate more platitudes to reinforce this theme. And, if I were a stringent Corbynista, I know where I'd be telling the consensus to go.
Jeremy Corbyn has an opportunity to seal a positive image of himself in the public consciousness, and to rewrite a polluted Labour brand as Mandelson did in 1994.
How he does this is another matter. He has few friends in the media, and fewer in the PLP. There has been no honeymoon period, and the Labour Party conference next week has an unnerving 'make or break' feel to it.
Can he win in 2020? Will he even last? I genuinely don't know. The last 18 months in British politics has shown that only a fool would be so sure.