Two parties suffered catastrophic defeats in the UK election – but only one of them is facing up to that | Martin Kettle

After a succession of victories, the governing party got a drubbing in the general election. This autumn, it must set out on the long, difficult road back. Some party members think something fundamental needs to change for success to return. Others seem adamant it was not the party that made the mistake, but the voters.

For many, the answer is not a change of direction. These supporters simply want a new leader, who they hope can do a better job of putting across what are, to them, the unchallengeable and thrilling truths for which the party stands, so that the scales fall from the eyes of the misguided voters. When Labour goes off the rails – and, look, they will say, there are signs of that happening already – there will then be a revival and everything will be hunky dory again.

What I have just said applies, of course, to the Tories, a party that still seems in denial about its predicament. Too many of its MPs and members kid themselves that choosing a true believer leader with “real Tory” views is all that matters. By comparison, the thought that the Tory party itself may also need to change receives vanishingly brief attention. The autumn Tory conference will be obsessed with the leadership race, which has now seen Priti Patel knocked out in the first round of voting, while neglecting the scale of the July defeat.

But I am not talking only about the Conservative party here. I’m also talking about the Scottish National party. The SNP got an electoral drubbing in July, too. Like the Tories, the SNP finds itself suddenly rejected in favour of Labour. Like the Tories, the SNP has been knocked out of its comfort zone.

The SNP’s annual conference concluded this past weekend. The difference between the way the SNP has begun, albeit inconsistently and sometimes disingenuously, to try to look the facts in the face, is a marked contrast to the Tory party’s general denialism. The Tories need to break that habit before it is too late. If they do not, the party may simply wither on the vine, much as the Liberal party did a century ago.

There were, inevitably, plenty of people at the SNP conference in Edinburgh who were in denial too. People who blamed the voters for Labour’s success in July, reducing the once hegemonic SNP to a nine-seat rump in Westminster. People who blamed the party’s hastily installed retread leader, John Swinney, for not campaigning for independence with enough passion. People for whom, as is so wearyingly frequent in the SNP, it is axiomatic to put all blame on Westminster – for which, far too often, read “the English”.

At the weekend, though, the SNP also began to do something that the Tory party seems incapable of doing. It had a postmortem. It asked itself what went wrong in July. Most important of all, it asked itself what it had done wrong. Not just done wrong in the six-week campaign, but done wrong in government too.

The answers were pretty stark. What’s more, they were delivered to the party faithful by the leadership themselves, rather than by external critics. Swinney’s keynote speech on Sunday afternoon ended in the obligatory upbeat style. But at times, and in important passages, it also accurately reflected some of the home truths that he had told his members in a closed session at the start of the conference last Friday.

That was when Swinney told the SNP what its own post-election polling showed. It showed how the party had lost the middle class (defined as people who earned anything above “the low £20,000s”). How it had lost its advantage among young Scottish voters (always in the past a key area of SNP strength). How it had governed in a way that had faltered (external critics would put this far more strongly).

He also admitted that the party’s behaviour had made it unpopular. That it had focused too long and too much on “the process of independence”. That it had sometimes treated the party membership with contempt. That it had underestimated Labour’s broad appeal. Once again, an external critic would have been fiercer, in particular about the obsession with immediate independence, the constant manoeuvring for a second referendum and the corresponding neglect of basic governing obligations towards voters with other priorities. An external critic would also have criticised Nicola Sturgeon’s habitual performative approach to politics more openly than Swinney was willing to do.

Nevertheless, this was sobering stuff for a party like the SNP. The party has spent years fostering an iron belief in its own wisdom. It admits to error as willingly or as often as Sinn Féin does. It has often behaved as if it were indestructibly popular, and as if its opponents were all indistinguishable traitors to Scotland, with views not worth listening to.

Related: SNP must focus on issues that matter to Scottish people, says John Swinney

Well, they had to listen at the weekend, at least for an hour or two. And it is a fair bet that the SNP will be a bit wiser and stronger for it. The SNP still has a daunting pile of problems, as a party and, even more, as a government, and it has been in power now for 17 years (see the announcement this week of £500m of spending cuts to come). Its chances of continuing that streak at the 2026 Holyrood elections have reduced, even though the proportional, and fairer, Holyrood electoral system means its numbers will not collapse as spectacularly as they did under first past the post in the general election.

Even so, the SNP’s future looks rather more promising than that of the Tories. It still has time, before 2026, to show it can govern better and behave with unaccustomed humility. And a lot of Scots still think Scotland should be independent. That has not changed. Scotland’s distinctly different political temper is not going to disappear. If Keir Starmer’s government falters or fails, that would send voters back to the SNP, even if not on the scale of a decade ago.

It is hard to say anything similar about the Conservative party. There has been no postmortem for the Tories, and no confronting the membership – or even the party leadership itself – with hard truths. Unlike Swinney, Rishi Sunak is nowhere to be seen, and gives the impression that he cannot wait to get out. Meanwhile the party hastens to repeat past errors. It is more exercised by the moving of a portrait of Margaret Thatcher than by the fact that it won only 8% of under-30s’ votes in July. A sensible person would insist that the Tories should stop, think and, for once in its modern history, learn something from Scotland.

• Martin Kettle is a Guardian columnist