The NHS bill cleared a legislative hurdle [2] in the Lords this week . But that doesn't really solve any of the political problems facing the government's reforms. Of those problems, one of the biggest is that the coalition doesn't seem to have a clear grasp of why Andrew Lansley's plans are causing so much difficulty.

The one thing everyone can agree on is that the plans have been appallingly presented. Lansley cooked them up in the Department of Health without much input or scrutiny from Downing Street. (So blindsided was the prime minister that the episode triggered a whole re-organisation of the Number 10 policy operation earlier this year.) According to one senior civil servant at the heart of the operation, when Cameron was first presented with Lansley's plan he skimmed the introduction and then turned to his aides in shock and disbelief and said "have you read this stuff?!" He had, until then, had no idea of the scale of what was being planned.

There was a moment, towards the end of January, when a u-turn was still an option. But Cameron feared looking weak by abandoning such a huge public sector policy drive - and, reasonably enough, worried that dropping the reforms would implicitly confirm voters' suspicions that the Tories had some hidden agenda on health. A u-turn would make it look as if they had been rumbled. The way senior figures in government tell the story, Cameron's foot hovered between the brake and the accelerator, finally choosing the latter. That now looks like a huge mistake.

The essential miscalculation was the PM's assumption that if he personally threw some weight behind the cause - deploying the powers of persuasion in which he has considerable confidence - the public mood might shift. Of course, the Conservatives did not count on a Lib Dem backlash, sanctioned from the top of the party as a device to "differentiate" the junior coalition partner (fearful of losing its identity) over an issue of famous toxicity to the Tories. Some of the Lib Dem turbulence around the NHS earlier this year was principled objection to the reforms but some is retaliation for the Tories' personal attacks on Nick Clegg during the referendum campaign on the alternative vote. The compromise package that ended up before the Lords this week was therefore a mangled monster consisting of the original Lansley plan with heaps of ad hoc Lib Dem caveats, brakes, disruptions and supposed safeguards.

And there lies the government's problem. The reform it is now trying to sell is the expression of Westminster political choreography and not a coherent response to the needs of the health service. Everyone in the NHS knows it and voters can sense it.

Cameron and Lansley have tried to sell the need for reform on the grounds that the health service cannot cope with rising levels of demand without major structural change (especially when there is no more money to fund the existing system). My own impression is that they haven't got that message across too well. One thing, however, is certain and that is their failure to persuade people of the follow-up assertion that the only solution lies in much more private sector involvement using much more vigorous competition to provide services. The Lib Dems and Labour are just as queasy about bald expressions of that view - it is, essentially, the Blairite model of public sector reform and has advocates in all three main Westminster parties.

But opponents of Lansley's plans don't need to rebut the theoretical premise on which it rests because (a) they can just accuse the government of unleashing needless revolutionary chaos in the NHS, which is plainly true and (b) they can accuse the prime minister of reneging on a pledge not to do (a), which is also true. Plus, (c) voters' mistrust of the Tories over the health service is visceral. Whatever it is the Tories are doing will raise suspicions of an ulterior motive; Cameron and Lansley have done everything possible to confirm that view by failing to sell the reforms on their own terms. You can't credibly insist that there will be no privatization of the health service when the core concept of the reforms is to promote more competition and more private sector involvement. OK, so it's not privatization in way that BT and BA were sold off in the Eighties, but it's hardly reinforcing the "national" in National Health Service.

The only way to actually persuade people that the Lansley plan is any good would be to sell the first principle of increased marketisation in health care but, implicitly, the Tories have accepted that such an approach is toxic to their political reputation. Besides, changes demanded by the Lib Dems have corrupted Lansley's vision enough that - even if it were the best way forward (which I doubt) - it can't be implemented as the health secretary envisaged. Meanwhile, there are £20bn of "efficiency savings" to be found, which will feel like cuts and inflation at around 5 per cent, which will have an impact on health budgets that will also feel like cuts. Every doctor and nurse in the country will have motive and cause to blame the government for every refused treatment and every bad outcome.

David Cameron needs to wake up to the fact that he has allowed a process to get underway whose long term outcome could easily be an historic reputation for him as the man who broke the NHS.