Political leaders search for big ideas without much success. After the whirlwind of Thatcherism and Labour's defeats in the 1980s cautious leaders hid behind tame, managerial language. What worked was what mattered. But the era of nervy, arid consensual politics is ending. Taking shape is a big ideological battle between two sides with very different views of society and the form it should take. For a long time we were waiting for big ideas. Suddenly two come along at the same time.
Ed Miliband's idea is tentative and embryonic, but its essence is clear. He believes government can be a benevolent force, protecting the squeezed middle and the poor from the riotous iniquities of unconstrained markets.
During the collapse of Lehman Brothers in the autumn of 2008, Miliband switched on the Today programme and heard an interview in which someone was urging government intervention on a massive scale to save banks, their investors and the rest of the economy. Miliband assumed the interviewee was from the left-of-centre Compass pressure group. It turned out to be a senior figure from Goldman Sachs. Such moments explain why he regards the ongoing economic crisis as an historic turning point, in which previously government-hating entrepreneurs plead for state intervention and the rest of the country wonder whether they are beneficiaries of the fruits of capitalism or victims without a protective shield.
In a period of maximum fragility Miliband argues that the rules must change. Bad firms must not flourish. Good ones must be encouraged. The undeserving wealthy will no longer be quite as affluent. The deserving wealthy will continue to flourish. In some form or other, the state must be an arbiter of what is and is not merited, what is good and bad. The state must also take a view on what is responsible and what is irresponsible conduct – from bankers to those who could work but claim benefits instead.
Miliband takes a very big risk but external events give him the chance to try out a populist approach. The banks are unpopular. When a private company runs a care home with reckless disregard for standards, Miliband's otherwise vague concepts feel more tangible. When Manchester City's Carlos Tevez is paid £250,000 a week and refuses to play, you wonder what crazed system is deciding who is lavishly rewarded and who is not.
There are obvious practical and political difficulties with Miliband's big idea. It is much easier to recognise a bad firm retrospectively than to devise rules in advance. Voters will be instinctively uneasy of being judged by government in whatever form the judgement takes.
The same is often said of Cameron's big idea, that his vision of the Big Society is vague. This is the alternative to Miliband's more active state. Cameron remains as committed to his big idea as he ever was. In a way that is striking, Cameron the seemingly pragmatic Tory likes advisers around him with an ideological streak. It makes him a more interesting leader than he sometimes seems. Cameron's senior adviser, Steve Hilton, remains an important player, even if he is a frustrated one. The big society – Hilton's passion – was the main theme of Cameron's conference speech a year ago and it will be at the centre of his address next week too.
Cameron's argument that there is such a thing as society but it is not the same as the state is the boldest attempt to re-project the Conservative party since Thatcherism. In some ways his big idea is what one aide once described to me as "reheated Thatcherism".
Thatcher also delivered speeches about how volunteers, charities and the private sector could replace the state. Cameron is more persistent and shows greater interest in outcomes. He wants to redistribute power to the lowest levels and is less concerned about accountability at the centre, a reason why he was – at first – entirely relaxed about Andrew Lansley's original NHS reforms. But the emphasis on the importance of improved delivery and the need for fairness is greater than in the 1980s.
Cameron's big idea is not an excuse for spending cuts. His advocacy began when he was pledged to spend as much as Labour. But he argues with the same conviction as Miliband that circumstances make his big idea more urgent than before. The state has less money. New ways must be found to deliver public services. Next week Cameron will argue that the Conservatives trust the people while Labour wants to boss them around. Cameron says he wants to give power to the people, not the other way around. "Power to the people" is always popular with the people.
There are, though, dangers and problems with Cameron's vision. For many it remains something of a blur. As with Miliband's big idea, the policy implications are not always clear. He functions in a fast-changing economic situation in which, while voters might theoretically welcome empowerment, they look to the state for security. These voters include not only bankers but reasonably successful companies such as Sheffield Forgemasters, which lost a government loan in the early days of the Coalition's cuts. Voters who notice the closure of libraries or Sure Start centres recognise the benefits of an active state and see no equivalent institution's appearing in Cameron's Big Society.
Miliband speaks of redistributing power too. Some in his shadow cabinet talk of a Big Society, the ultimate tribute to a political opponent. They believe Cameron is on to something, although I doubt if Miliband does. Similarly Cameron and George Osborne are sensitive to the dangers for them of the moral populism that Miliband articulates, even if they regard him as a weak political opponent who moves his party away from the theatrically managerial politics of Tony Blair, the figure they most revere.
If Miliband can portray Cameron/ Osborne as figures from the past, as outdated as Blair, his big idea has more chance of taking hold. If Cameron can pull off the balancing act of projecting his Big Society as a genuinely effective alternative to a well-funded state, Miliband will be doomed to defeat as a backward-looking statist. The last time there was a battle of ideas, in the 1980s, Labour was slaughtered, which is why New Labour opted for the safety of the Third Way, meaningless but unthreatening. I spoke to some activists at Labour's conference on the night of Miliband's speech who feared another slaughter next time. And yet Cameron has promoted his vision for a long time without breaking through.
During the managerial phase of politics a lot of nonsense filled the ideological vacuum, simplistic rubbish about "spin" and "trust". The next election will be decided by a battle of ideas. Good.
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