Nothing makes people angrier than losing their position in the world to someone they feel deserves it less. We've seen the wrath of the white working classes over losing their jobs and their council flats to immigrants. We're about to see the fury of the middle classes losing their university places to poorer students with worse qualifications. What Labour unleashed on its supporters in the last decade, the Tories are inflicting on their supporters in this one.
In the next round of university applications, admissions officers will have to take into account the average GCSE and A-level results of the candidate's school and the proportion of pupils in their neighbourhood who go on to higher education. The Ucas form already asks whether a candidate's parents have a degree. The idea is that an applicant from a poor school or neighbourhood can then be offered lower grades. Universities will be able to spot potential as well as achievement, and make allowances for bad teaching.
At least, that's the idea. But if a school is selective, and a bright but poor child has managed to pass the stringent entrance exam at 11, why should he or she be penalised for coming from a school which has good results? Of course it has good results: it has pupils from only the highest ability range. That doesn't make the pupils undeserving.
For the most elite universities, there is a problem too. The new A* grade was introduced last year for A-levels, in an effort to mark out the very brightest pupils. It is impossible to do better than to gain A*s in every A-level. Yet even now, there are privately-educated pupils being rejected from Oxbridge despite being predicted an A* in every single subject. One I know was also head girl of her school and in a national sports team. What more could she have done to show her potential?
You don't read about these sob stories yet, for the papers are still full of Laura Spence-style case studies: bright children, preferably black, from state schools, who didn't win an Oxbridge place. And yes, of course they should have their background taken into account. But don't underestimate the power of the political backlash, the sense of betrayal among middle-class voters, when more and more of their children are rejected despite having tip-top grades.
For the positive discrimination is not just going to hit the privately educated. It will apply to anyone who lives in a reasonable neighbourhood or goes to a reasonable state school. The better a school does in the league tables, the lower its chances of getting its pupils into a good university. What incentive will there be for it to improve its students' results? It would do better to encourage its less able children, who aren't destined for higher education, to work less hard so as to bring down the average grades for those who are.
Perverse incentives driven by league tables are what have got us into this mess. Because schools are encouraged to maximise the number of pupils winning five A* to C-grade GCSEs, they tend to concentrate on children at the boundary between D and C and neglect the brighter ones who are going to pass anyway. If there were also a target for As and A*s, the children with high potential would be much better prepared for top universities.
The problem lies in the schools which, as a recent Policy Exchange study found, simply aren't stretching the ablest pupils. Until they are sorted out, though, there is an argument for giving disadvantaged children a bit of a leg-up. It's not their fault, after all, that their teachers haven't focused on them. And they have only one chance in life.
But don't let's pretend there won't be losers as well as winners. If universities aren't expanding, this will be a zero-sum game. For every poor student who wins a place, a middle-class student will fail to. For parents whose chief goal for their children has always been to get them into a high-ranking university, this will be seen as catastrophic.
An Oxford professor was moaning to me the other day that many of the brightest Oxbridge rejects will go off to American universities. And they won't come back. Their talent will be lost to this country. At least they won't be around to vote against the Tories out of pique. But their parents and grandparents will.
It was the zero-sum game nature of immigration that made working-class Labour supporters so angry. There is only a limited supply of council housing and a limited number of places at good local schools. The jobs market is no longer expanding, and even when it was, employers could afford to offer lower wages because there were enough immigrants willing to work for less. A 2008 study by Dustmann, Glitz and Frattini in the Oxford Review of Economic Policy found that each 1 per cent increase in the share of migrants in the working-age population led to a 0.6 per cent fall in the wages of the lowest-paid workers but an increase in the wages of the highest-paid.
Both the working and the middle classes are particularly aggrieved because the phenomena they are facing are irreversible. Barking and Dagenham will never again be white working-class suburbs where neighbours have known each other all their lives. Maybe that's inevitable, but it still hurts. Equally, middle-class teenagers who have bust a gut to get top grades at school but still don't make it to an elite university will have to live with that forever. So will their parents.
What it comes down to is that we're all in favour of upward mobility, but nobody likes its obverse. In an economy which is booming or a university system which is fast expanding, it may be possible to have upward mobility at little cost, by simply increasing the number of jobs or places. One person's opportunity is not another's loss of opportunity. Now, though, it is.
And the oddest thing is the role reversal of the political parties. Labour's wave of immigration was great for the middle-class employers of nannies, plumbers and decorators, but dismal for the unskilled and semi-skilled Labour supporters who found themselves out of a job or forced to work for less. If they had a family to support, they often could not manage on the lower wages on which a single Pole could afford to subsist.
Equally, David Cameron's support for positive discrimination in university places will hit his own supporters hardest. Those voters who believe in aspiration, hard work and doing the best for their children will be overtly penalised by a Conservative government.
It's a funny old world when political detoxification has come to this. Labourministers were so desperate to be seen as business-friendly that they sucked up to the bankers and allowed in loads of foreign workers. The Tories are so desperate to be seen as compassionate that they have gone far further than Gordon Brown ever did in forcing universities to transform their intake.
Politicians may say, privately, that their own voters have nowhere else to go. Well, at the last election, many Labour supporters either stayed at home or voted BNP. Tory voters may be equally mutinous at the next. They could vote Ukip or simply not vote at all. Cameron should be under no illusions. He is going to create bitter enemies among his own kind.