People like me have been moaning for years about how all the parties are the same at Westminster, crowding the centre ground and pursuing synthetic focus-group policies. But this week, as the Conservatives respond to Ed Miliband, we are going to see something different. A gulf in policy and ideology that, on the surface at least, looks as wide as anything we have seen in the last two decades.
David Cameron will attack Ed Miliband's plans to freeze energy prices, build 200,000 houses a year and scrap the bedroom tax as a lurch to the left. Tory ministers will accuse Labour of the politics of envy for wanting to extend the bank levy, introduce a mansion tax, axe higher-rate pension tax relief and possibly restore the 50p tax rate. Worst of all, with Ed's threat to confiscate development land, end NHS privatisation, selectively increase the minimum wage and curb bank bonuses, the Labour leader will be accused of taking Britain back to the bad old days of the 1970s; of class war, nationalisation and state controls.
That is far from the case. However, before deconstructing "Red Ed", a word in defence of that much-maligned decade. Fashions in the 1970s may have been execrable and industrial confrontation was out of control. But Britain was at its most equal, in terms of income and wealth, in 1977. It was an era of genuine social security, when houses were cheap, jobs were relatively abundant, Britain was an industrial nation, and there was genuine social mobility thanks to free higher education. Unemployment was thought to be excessive when it surpassed one million.
Countries like Germany and Norway have stuck essentially to 1970s consensus politics with great success. Britain left for the far side of Thatcherism and ended up with a dysfunctional economy dominated by a banking kleptocracy. But in our deracinated political culture, under both New Labour and the Conservative coalition, the bogey of the 1970s has been used to close down political debate, in England at least.
In Scotland, the SNP adopted Labour's social democratic agenda almost wholesale - unilateralism, abolition of tuition fees, social housing - and has been successful, electorally at least. So successful that Ed Miliband wants to steal some of it back.
But the Labour leader's radicalism is heavily circumscribed. He is not proposing a fundamental shift of wealth and power, nor will he back his conference on public ownership of rail and Royal Mail. He said nothing about nuclear weapons and isn't proposing to redistribute wealth or restore the principle of free education. Miliband is responding to the despair of Middle England as it discovers it is no longer the poor who are being squeezed.
The general decline in earnings since 2008 has masked a profound shift in British social demography. With student debt, house prices and the collapse of the old career structure, the aspirant middle classes of the 21st century are discovering they no longer have a foothold on prosperity. The old distinctions between the middle class and the working class, as in that old Frost Report sketch with John Cleese, Ronnie Barker and Ronnie Corbett, have eroded.
This is why Labour is banging on about the "cost of living crisis". That is something the working poor have always suffered, but now it is spreading across the social divide, leaving a gulf between "us" and a super-rich 1% "them". "Red" Ed has realised that this has revived the market for elements of the old social democratic consensus. His targeting of the energy companies is no accident: high energy costs hit the middle classes disproportionately because they have larger houses.
Whatever you think of Miliband's qualities as a leader, he has an astute understanding of political dynamics. He has drawn a line under the New Labour experiment and rediscovered the rhetorical power of fairness. Getting both the profiteering energy companies and Peter Mandelson to disown him in the same week was pretty good going. And this week, the Conservatives will be left defending the indefensible - bankers, energy bosses, property developers and people who live in £2 million houses.
But what does it mean for Scotland? Well, it could mean the SNP has a fight on its hands. If there appears to be a genuinely left-of-centre party bidding for power in Westminster, the argument that Scotland needs independence to secure social objectives is undermined. It is too early to tell yet because the Scottish Labour Party under Johann Lamont has moved in the opposite direction by defining her leadership through an assault on universal benefits. But the Nationalists may no longer have all the best tunes.
Voters in Scotland often despair at the tribalism of politics. On social housing, bedroom tax, green energy, NHS, apprenticeships, gay marriage and living wage, Salmond and Lamont are on the same side. Much of their mutual antagonism can be put down to the fact that Scotland used to be effectively a one-party state. If you wanted to get on in Scotland, in public-sector jobs, local government, quangos etc, you had to join the Labour tribe. This power of patronage has been destroyed by two SNP governments and the destruction of the Labour electoral monopoly of local government - though ironically it was a Labour first minister, Jack McConnell, who sealed their fate by introducing fair voting in council elections.
I don't think Alex Salmond will be losing too much sleep over Ed Miliband's rediscovery of social democratic rhetoric. The Labour leader's ignorance of Scottish politics was revealed by his suggestion the NHS might be split by independence. It is already split, thanks to the Tory reforms - and in Scotland the SNP Government has defended the integrated National Health Service that Ed Miliband says he wants for the UK as a whole.
The SNP will only find itself challenged if the Scottish Labour Party discovers its voice, shakes off its antagonism to popular policies like tuition fees and stops behaving like the party of the council bureaucrat. And there is no sign yet of that.