It is remarkable, is it not, how much “wisdom” about UK politics has been received and then jettisoned in four months. Before the election it was taken for granted that we would have a hung parliament. The rise of Ukip and the SNP apparently made a majority government arithmetically impossible, even though our first-past-the-post system had produced majority governments since the war.

Then there was the colour of the supposedly inevitable coalition. The same number crunchers said that only Labour would be in a position to lead it; the Conservatives limbered up for a leadership contest. It was soon clear, however, that the UK electoral system had reverted to type and David Cameron was pretty much the only party leader left standing. Boris Johnson and Theresa May could spar only about water cannon.

But is it only the electoral system reverting to type? Or could something similar be starting to happen with the political parties, too? The course of the Labour leadership contest suggests this might not be so, with implications for all three parties, the Liberal Democrats included.

After initial disbelief at the scale of Labour’s defeat, those who studied the debacle – whether from inside or outside the party – lost no time in pinning the blame on Ed Miliband. They said he had been personally unconvincing as PM-in-waiting and that he had got above himself – his Ed-stone had been Neil Kinnock’s Sheffield rally. Above all, though, he was blamed for spurning the advice to campaign from the centre and taking Labour to an unwinnable position on the left.

Blairites past and present, and even the man himself, seized the New Labour explanation and ran with it. If only the party had campaigned on different policies: more aspiration, more fiscal responsibility, more vision. If only it had had another leader (for another, read the other brother). Labour, they convinced themselves, really could have won.

Yet those who blame Labour’s defeat on Miliband’s supposed old-fashioned leftism have to confront certain realities. Labour was routed in Scotland by a party that not only appealed to nationalism but professed policies a good deal further to the left than Miliband’s. They must also acknowledge that the response of at least some Labour voters outside Scotland to Nicola Sturgeon’s debate performances was to wish that she was their candidate. Strip out the Scotland-first aspects of her pitch (which was easy to do) and you had a coherent – and traditional – socialist world view. Blairism may have its electoral virtues, but ideological consistency is not one of them.

Some might argue that in some parts of the country once Labour voters moved to the right in defecting to Ukip (so letting the Conservatives in). But were those voters consciously veering to the right, or were they rather looking for a party that seemed to represent their interests in the way that old Labour had done and neither New Labour, nor Miliband any longer did?

The results of the Labour leadership contest when it finally happens – if it happens, given the scare-mongering about “entryism” and other deviancies – should show how sentiment in the party breaks down. And it may be that the grassroots turns out to be profoundly Blairite after all.

But maybe not. And even if Jeremy Corbyn’s surge fades, his unpredicted following – so unpredicted that some MPs nominated him just to make a contest of it – suggests there is a constituency for a Labour party that is further to the left than New Labour, perhaps even further to the left than Miliband dared to go.

Such a Labour party would be more egalitarian, keener on the public sector (and what is seen as its particular ethos), more concerned about job security and decent social housing, open to reversing the tide of deregulation, with renationalised railways, a renationalised water industry and heavily regulated energy utilities, and (it almost goes without saying) much toughness on bankers. It would also be less captivated by the City of London and more internationalist, though less interventionist, in foreign policy.

Such a Labour party could, of course, precipitate a schism of the type that produced the SDP in 1981, which would demonstrate, in turn, how electable a leftist Labour party would be. But it is not at all clear to me that the Scots are alone in favouring an older type of Labourism. After all, the voters in many European countries do too, where they call it socialism.

But there need not be any schism. Another consequence could simply be greater differentiation among the parties, as Labour re-occupied its earlier space and Blairites considered where else to go.

It may be that the grassroots turns out to be profoundly Blairite after all

And here it is not just the Daily Telegraph’s “Tories for Corbyn” who should be backing the Labour left-winger in their own self-interest. Whether or not they think it worth £3 to take part, the Liberal Democrats should be rooting for Corbyn too. Not because a more leftwing Labour party would necessarily push Blairites in their direction, but because Corbyn-style clarity about what Labour stands for would help the Liberal Democrats to define themselves more clearly – and they could start by giving full meaning to both elements of their name.

I am not one of those who believes it was a mistake for the Lib Dems to go into coalition – either at all, or with the Conservatives. The coalition was a better government than it was often given credit for, and only two months into a Conservative-only administration, the value of the Lib Dems’ constraining influence is already apparent. But the consequence, as for any junior coalition partner, was a blurring of the edges, a loss of distinct electoral identity and near-destruction at the polls.

A return to more leftwingery for Labour could create more ideological space for the Liberal Democrats and foster a stronger electoral identity for both parties. But the disaggregation of British politics would not necessarily stop there. Before the election, many Tories openly hankered after olden days. They could well renew their clamour, once the victory glow wears off and the Europe referendum looms. The chief beneficiaries of more vacant centre ground would again be the Liberal Democrats. The only question then would be whether Tim Farron had grown into a leader able to capitalise on liberalism’s new appeal.