In the circumstances it was probably just as well that David Cameron ended his speech launching the government's detailed programme by making clear that he is, in fact, a Conservative and that Nick Clegg is, indeed, a Liberal Democrat. So much else has been turned on its head in British politics over the past two weeks that it is a comfort of sorts to know that a few things still remain the same.

Do not rely on even this remaining true indefinitely, however. Since 6 May there have already been plenty of days when one pinches oneself to be sure the whole process of coalition is for real – the talks, the handshakes, the garden press conference, the new cabinet, Cameron and Clegg side by side on the frontbench when the Commons reassembled on Tuesday. In many respects, though, today topped the lot.

Cameron's and Clegg's 36-page programme for government is not for show. In fact it's certainly for real and it may be for keeps. As the two men say in the introduction, theirs is a historic document. British governments do not normally set out their five-year plans in this way with carefully written pledges under 31 separate detailed headings. Such things are normal elsewhere in Europe, where coalitions are routine. For Britain, by contrast, this is unprecedented governmental programme transparency, a step forward, real grownup, nitty-gritty stuff. Danny Alexander and Oliver Letwin, who jointly did the heavy lifting, should take a bow.

The content matters most, of course. Many of the key elements were known already – emergency budget, autumn spending review, tax priorities, Trident, Europe, political reform – and were set out in the earlier coalition agreement on 12 May. Today ties that earlier document down. Its most important sentence is almost certainly the one inside the back cover making clear – as George Osborne underscored – that the deficit reduction programme trumps everything else in the agreement.

Nevertheless there is also plenty that is new, including big topics largely unaddressed in the earlier agreement like crime and policing, business, equalities, and the health service. If the 12 May document dealt head-on with the subjects that needed resolution before a coalition could be agreed, this week's larger version fills out the gaps. There are omissions nevertheless. There is still barely a mention of the arts. The fate of Ofcom and dozens of other agencies of varying importance is not revealed.

It is easy to be dismissive and a lot of people are. There is a lot of continuity with the past – more than it suits either the coalition or its detractors from admitting. Large tracts of the agreement are also aspirational rather than achievable. More broadly, the idea that any government, especially one composed of such sometimes uneasy bedfellows, can ever truly command the political agenda is a vanity. This government, like those before it, will be shaped at least as much by events as by its own programme.

An emerging critique today was that many difficult problems have been sublet to commissions and reviews. My count is 33 such issues, ranging from the massive, like long-term care, public sector pensions and local government finance, to the more manageable, like extradition, non-doms or Scottish fossil fuel levies. A lot of criminal justice issues have been parked in this way, like sentencing policy, criminal records and legal aid. The assumption is that nothing will happen quickly on many of them. But in grownup policymaking about difficult issues it often makes sense to step back and make progress gradually, especially after Labour's compulsive legislative hyperactivity. And with money in short supply, grand schemes will in any case have to wait.

These are still very early days. For the coalition, necessity was at first the mother of invention. Before 6 May, both partners gave some hypothetical thought as to how they might work together (and with other parties). All the real work, however, has been done in the past two weeks, since the logic of the parliamentary numbers became clearer. Yet it is not too soon to insist that almost everything about this government so far, including today's programme, is intended to be about more than making the best of a bad job.

Everything now points, indeed, to this coalition being a serious historic attempt to realign the liberal centre-right in the electoral middle ground. Cameron and Clegg, in their own ways, now almost say as much. "The more I see of this coalition in action," Cameron said, "the more I see its potential, not just in solving the problems that lie before us but solving them with a shared set of values". Clegg went even further, seeming to claim that the coalition's compromises and differing traditions – he now routinely talks about the "blend" between the Lib Dems and the Conservatives – have made its programme even stronger than they would have been apart.

Make no mistake about this. Cameron and Clegg have suddenly become unexpected partners in a major political enterprise, not just to master the next five years of British politics but to reshape the party political map for a generation or more. Clegg's coalition decision last week was certainly a fateful call for the Liberal Democrats, but the palm for political audacity in May 2010 belongs above all to Cameron.

The Tory leader is exploiting every opportunity the political situation presents him to drag his party rapidly towards the liberal centre. I believe in leading from the front, he said, and he is telling the truth. The many policy concessions to the Lib Dems, especially those which cauterise the Tory right's pet issues like Europe, the Human Rights Act and inheritance tax only make sense in that light. The right's indignation is eloquent proof of what is happening. The control grab over the backbench 1922 committee is the work of a politician who is set on marginalising the right, the mirror image of Tony Blair's approach 15 years ago.

Will it succeed? Much depends on the impact of the budget and the spending review. There may be coalition tears before bedtime. But, if not, there is an intriguing alternative. Four years down the line, if the economy is reviving and the liberal programme is secured, will the coalition partners run against each other in 2015, or will they be tempted to run for the coalition's re-election? An electoral pact to support one another under the alternative vote system would make a lot of sense. If that happens, then the May 2010 political realignment could last for a decade and more.