Precisely because they are conservatives, supporters of the Conservative Party have traditionally been a pretty reliable bunch. That is, they could be relied upon to vote Tory. All parties have their loyal supporters, of course; indeed, in some cases, such as Jeremy Corbyn’s acolytes or the most fervent Nationalists, it can sometimes more closely resemble religious mania than loyalty. Conservatives don’t usually go in for that sort of enthusiasm, which isn’t a terribly conservative trait. But the fact that they prize loyalty, and show scepticism about change and innovation, used to mean that, even just counting on inertia alone, the party could count on considerable support.

That’s part of the reason why they have been in power for a sizeable majority of the past century, and until recently could be described as one of the most successful political parties in the world. Not any more.

The rank and file are deserting the party in huge numbers. The most recent ComRes poll put the Tories on just 23 per cent. Even if that is an underestimate of their support, it’s catastrophic. And not just for Conservatives – since one of the likely consequences is that Jeremy Corbyn will become prime minister, there will be plenty of adherents of other parties who will view it as an unmitigated disaster, even if they hate the Tories.

The obvious cause of this decline is Theresa May’s failure to deliver Brexit – something which seems to be confirmed by the rapid and substantial rise in support for Nigel Farage’s new Brexit Party (helped, no doubt, by the fact that Ukip has moved from being a party of politically incorrect dogwhistle racists, at least paying lip-service to the idea that being racist is a bad thing, to being one of out-and-out, unapologetic racists). But it’s possible that the failure of Brexit has actually helped to disguise all the other failures of Mrs May’s tenure – that so much attention has been paid to her inability to deliver on the EU that we’ve not had time to notice how abysmally badly everything else has been handled.

On Brexit, it is possible to argue that it’s not all Mrs May’s fault. Any other prime minister attempting to deliver on the result of the referendum would probably, given the intransigence of both Leave and Remain camps, the complexity of disentangling the UK from EU bureaucracy (even if you count that a point against the EU) and the current composition of the House of Commons, have had a hard time and very possibly failed. That’s not to let her off; she’s failed more abjectly than anyone else could have contrived to, and created all the reasons for failure herself.

The fact that the Tories are divided on the EU doesn’t help, but it’s not the reason they are in such a terrible state. The Labour Party is just as divided on the subject. In any case, both the large UK parties have long been broad churches on other issues too; just as the Conservatives could until recently accommodate both Anna Soubry and Steve Baker, Labour had opinions ranging from Kate Hoey’s to Chris Williamson’s.

Tory differences of opinion on the EU are not new, nor are they the root of their travails. It is that grassroots Conservatives regard the Government as having failed on two grounds quite separate from Brexit.

The first is that the party has failed to succeed electorally, and in terms of being judged minimally competent. This is a crucial requirement for Tories; the last implosion of the party, during John Major’s government, is often regarded as having been caused by the rise of Euroscepticism. But that was a side issue; it wasn’t chiefly the approach to, or mishandling of, the ERM that did for them (and put them out of office for years), but the fact that the economy tanked. In the face of being viewed as “the nasty party” or uncaring, Tories had previously been able to point to the fact that the economy was usually in better shape, and more people better off, at the end of each of their terms in office, while every Labour government in history has left office with the finances in a worse condition. The Major government’s cardinal sin was to fail that test.

The economy may not be ruined yet, but in almost every area of public policy, the record of the current government hardly looks like one of achievement. Universal credit is being introduced remarkably ineptly; HS2 and Crossrail remain expensive unfinished vanity projects, and the Windrush generation deportations (largely the result of Mrs May’s time in the Home Office) rightly received condemnation. But it’s not just that these are bad, or even cruel, policies. It’s that they’re not even competently handled.

The other failure, from a Conservative point of view, is that the Government is not conservative. The sugar tax is merely the most obvious example of the kind of technocratic authoritarianism most Tories detest, but the inclination to meddle and to micromanage has been a hallmark of Mrs May’s leadership. And anyone who thinks that there has been a drift to the Right (always to be called the far-Right) in British politics should examine the independent assessment of Mrs May’s unsuccessful manifesto as the Tories’ most Left-wing policy stance since 1964.

Tories can put up with quite a lot of this; David Cameron was viewed by many Conservatives with suspicion, and many of them found his stance on a number of issues dangerously pinko. He failed, for example, to do anything for rural Tories who had backed the Countryside Alliance, though he listed it as his first priority before he was elected. But he got elected, so they were prepared to put up with it, just as some on the Left of the Labour party tolerated Tony Blair while he kept winning elections.

The difficulty is that Mrs May is a failure as a Conservative, and also a failure as a competent, election-winning politician. And replacing her probably won’t even help. Her legacy is to not just to have failed to deliver Brexit, but to have put the Tories – if they even survive as a united party – out of office, quite possibly for longer than the period after Major’s fall, and perhaps for a generation. And they deserve it.