There are few things more exasperating than a universal phrase constantly and repeatedly deployed as though it was an expression of unique and final wisdom. “They just don't get it” is one of those. One understands what is meant, of course. The “they” is MPs and the “it” that they just don't get is how angry we (ie, everyone else from the humblest BBC presenter to the mightiest nurse) are about their expenses.

But let me put another suggestion to you, which is that just about nobody gets it; that just about everybody doesn't really understand how we got to this situation, or comprehend in any useful sense what it really means. Especially anyone who says “they just don't get it”, or the broadcaster's version of this, “Do you understand why there is so much public anger?”, as if the broadcaster was any the wiser.

Well, on a positive, if repulsively arrogant, note I have to tell you that, as of this week I exempt myself from being a member of this ignorant majority group. I think, at last, I have got “it”, and today I am going to spread a little of “it” around.

On Sunday morning I took part in a nice BBC programme, and - while I was waiting to do my bit - listened to a prerecorded interview with the historian of postwar society and politics Peter Hennessy, several of whose books reproach me from the shelves as I write this. My paraphrase will be inadequate, but this is the remembered gist: today's politicians aren't as good as yesterday's, and that's why we have an expenses scandal and why trust is at a record low. Simply return to Cabinet government and re-empower civil servants, and all will be weller. And as I sat there behind the green mike with my headphones on, I said to myself: “Even he just doesn't get it!”

Hennessy - one of the best brains we have - suddenly reminded me of what gets said about footballers and A levels, neither of which are supposed to be of quite the standard they once were. But the truth is that football is far faster and more athletic than it was in the halcyon days of Blanchflower and Wright; it is quite likely that the Fulham of today could beat the Arsenal of 1970. What has changed about A levels is the standard of teaching to the examination - far, far higher than when I took them - and the weight they have to bear as indicators of a youngster's ability. The children aren't stupider; if anything they're cleverer.

And politicians aren't worse than they were. What has happened is that politics - the circumstances in which politicians do their work - has changed profoundly in the past 40 years, without anybody quite realising. If Mr Attlee, a particular hero of Peter Hennessy, were PM today, he would be toast by teatime, consumed by the 24/7 media culture and the myriad forms of high-speed scrutiny to which today's leaders are subject.

The missing link in my understanding was provided by John Keane's new history of democracy. Keane's thesis is that the simple system of representative democracy has been overtaken, gradually replaced, by what he calls “monitory democracy”, in which power is open to continual challenge and scrutiny, to the growing discomfort of those who exercise it, or hope to. In recent times we could point to, among many others, the Human Rights Act, the Freedom of Information Act, the Data Protection Act, Sir William Macpherson's inquiry into the death of Stephen Lawrence and the Hutton and Butler reports, which revealed between them more about the intelligence services and the internal operation of government than we had ever been privy to before. The likely publication of Cabinet minutes on war in Iraq will be just another inevitable part of this process. Attlee did not have to deal with this.

The personal lives of those in power have also, in this time, become the stuff of scrutiny, from David Mellor's over-the-gate rictus of reformed husbandhood to Jacqui Smith's porn film humiliation. Until recently I saw these as phenomena separate from the demand for open information, but now I “get it”. They're part of the same process.

At the same time politicians have increasingly been deprived of the automatic support of their tribe or social class. Now they are judged on results, on performance, on demeanour - without any agreement on what success constitutes. Their party support has atrophied as the size of political parties has diminished, and as the burden of national political action is carried by fewer and fewer activists. Even giving those activists a vote for the party leader (unimaginable in Attlee's day) has failed to arrest the decline. Few of us are “political” but most of us are “monitory”.

Unaware themselves of what is changing, MPs encounter us as hyper-critical, unreasonably demanding and seemingly apathetic. And this may explain something else. The editor of the BBC programme had noticed, in Chris Mullin's recently published diaries, a reference to a discussion in a parliamentary committee concerning the possible publication of MPs' expenses. It was May 1, 2002 and Mr Mullin quotes the Leader of the House, Robin Cook, as saying: “We are in a jam. Few members have tumbled yet to the juggernaut heading their way.”

There is usually a reason for denial. I wonder whether MPs' surly, resentful refusal to reform their expenses has its origin in something rather simple: a repressed hatred for the voters. Can you imagine the adamantine ego it would take to face all that abuse and whingeing from those whose support you seek, and not feel murderous?

Comedians, the writer John Lahr has written, have the same feeling of disdain for their audiences. You wouldn't believe how nastily even much-loved comedy hosts speak of their publics. In the case of MPs, the hatred is more than reciprocated, as the worrying comments below the online version of Julie Kirkbride's Times article last week show. We think they're crooks, bad mothers and crap adminstrators and say so - they think we're a bloody shower, but have to keep shtoom.

Yesterday some plausible Lib Dem speed-merchant was saying, a propos of political change: “People know what needs to be done, let's get on and do it.” It was utter rubbish. People don't yet know what needs to be done, because they don't know what is wrong, because they don't really yet understand how things have changed, because they don't get it. Except me. And now, you.

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