Will spending cuts have to assault middle-class voters?
The welfare state has never been successfully rolled back.
That is the blunt conclusion Emeritus Professor Howard Glennerster has reached after spending a working lifetime studying it.
He has seen governments come and go - some hostile some keen.
And every failure to row back the state has its reasons.
Sometimes it is a changing population - the massive rise in school-age children after the baby boom, for example, that sent education costs soaring; or the increase in the numbers of the elderly; or the high unemployment of the 1980s.
Short-term containment is as much as anyone ever achieved, former Prime Minister Margaret Thatcher included.
And what is Prof Glennerster's analysis of the task facing the coalition?
"The challenge is to threaten the interests of the median middle-class voter on whom the Conservative Party and the Liberal Democrats depend. Only by challenging their core vote, it seems to me, can they deliver."
Will the coalition confront the voting power of its own supporters? Why should it?
Prof Glennerster, a specialist in social policy at the London School of Economics, continues: "This is a battle to stop the middle classes assuming that the state is there to provide for their university education and comfort in old age."
Universal no more?
The debate about the public finances has so far concentrated on the question of fairness to the poor, but should it be about the middle classes?
The arguments for a shift of focus come from all sides. For Analysis on Radio 4, we asked four politicians from across the spectrum to tell us how to cut the infamous deficit, basing their ideas on consistent principles.
The thrust of their answers was fascinating.
First up, for three of the four, was ending universal benefits. These are paid regardless of people's means, like child benefit or, for pensioners, the winter fuel allowance, free TV licences or free bus passes.
Concentrate what you have got on the poor, we were told, and so, by implication, take it away from the better off.
On the right, the argument was that the cause of greater self-reliance - and lower tax - justified forcing people who can to look after themselves. On the left, it was a question of prioritising those in most need.
But that is small beer compared with what followed. Even the core state pension itself came under attack.
This too is a universal benefit, but one that the coalition has made substantially more generous.
The government's argument is that if people see their state pension reduced as soon as they save for themselves, they will not save, so the state pension cannot be means-tested.
But to make it more generous for all is hugely expensive - and that is a large part of the reason for the rising retirement age.
Less well known is the calculation by the Pensions Commission of how high the retirement age would have to go to make the arithmetic work. The answer: 73.
That would be one way of paying the price of persuading people who can to save for themselves rather than rely on the state. It is a price paid by all, either in years, or in tens of billions of pounds, for preserving middle-class entitlement.
The potential costs of long-term care for anyone who might be thought to have the income or assets to pay for it themselves will be another big pressure.
So will university - from which the middle classes benefit most. It will have to cost more, says Kitty Ussher, a former New Labour Treasury minister. Hitherto, university-goers have been subsidised at the expense of people who do not go - often the poor, she said.
Who will defend the middle classes? Do they not deserve to get something back?
One hope is that efficiency will deliver everything they want from the public services, while cutting what needs to be cut - an argument that so divides believers and sceptics that each scoffs at the other's naivety.
But, among our panel of four, the staunchest defender of middle-class entitlement turned out, believe it or not, to be old Labour's Roy Hattersley.
The former Labour deputy leader told us that universalism - whether in welfare or the public services - was essential to maintaining the consent of the better off who overwhelmingly pay for it. "Services for the poor are poor services," Lord Hattersley said.
But does that turn services for the better off into little more than a bribe to keep them in the welfare state club?
There was only area for our contributors where there was real unease about challenging middle-class entitlement: healthcare. But some is already means-tested, like dentistry or eye care: free for some, charged to others.
And that could be extended, to systems of co-payment for non-urgent treatment, for example. But there was no rush among our four to suggest it.
To the question of why the welfare state has taken an ever-larger share of national income for the past 60 years, the answer seems obvious: public and political demand.
If demand for what the state does cannot be contained, nor can the bill. But who, really, has been most demanding?