Governments tend to run out of juice halfway through their term. The fizz and sparkle goes out like an unswigged glass of champagne at the end of a very long Bullingdon club dinner.

Ministers are run down by the daily infighting – not just with colleagues from the same party. Governing parties lose byelections to the opposition. Factions emerge: in the Conservatives we see the Tory friends of UKIP, while the Liberal Democrats ponder dumping Nick Clegg.

The effect on the ship of state may be dramatic – potentially leaving it rudderless amid a storm of cuts and policy changes. The worry is especially acute for the NHS, which accounts for almost a quarter of government spending, and faces the challenge of an ageing population, rising patient expectations and expensive new drugs.

The King's Fund today publishes its own mid-term assessment of where the NHS is and where it is going. While it appears to be holding up, the thinktank warns "cracks are beginning to appear", which the Guardian's survey of healthcare professionals seems to back up. Waiting times are creeping up, while hospitals are struggling with their finances, says the King's Fund report.

Even more worrying are the downsides of the reforms, which the report highlights. Take the 200-odd clinical commissioning groups – essentially bunches of GPs – that will buy care and treatments for their patients from April. The King's Fund says these might be worse than what went before – and could struggle to change patterns of hospital usage.

It is not news, given the proliferation of new bodies, that the coalition's health system will be even more complex than the one it is replacing. However, the report is peppered with warnings that there is "a real risk of regulatory failure" in the upheaval.

So ministers have to be able to work together to ensure the system does not fall apart at the seams while trying to make £20bn in savings. So far, there's been the sound of good intentions, especially over social care, from both Tory health secretary Jeremy Hunt and Lib Dem health minister Norman Lamb, but little cash or policy.

Elderly care remains a huge issue for the NHS and the King's Fund notes "with further cuts to local government in the pipeline, there is likely to be a deterioration in the care of older people and people with disabilities".

It is the issue of cash that is likely to split the two parties. Hunt has already indicated that the NHS might not see rising budgets forever. This might already be the case – given that the Department of Health is handing back billions to the Treasury. Under Andrew Lansley, the last health secretary, the talk was all about recycling savings. Now it's about funding the deficit.

This could be toxic for the coalition. Lord Ashcroft's polling shows Labour has a lead of 25 percentage points over the Tories on the NHS and of 37 points over the Lib Dems. The two coalition partners will be defending a shared record on the NHS at the next election. Since incumbent governments win or lose elections mostly because of what they did; it's unlikely that blue- or yellow-rosetted candidates will be able to tell vastly different stories on the health service. That allows Labour to plot a populist and distinctive NHS policy – which at the moment appears to rest on the Napoleonic maxim: never interrupt your enemies when they are making a mistake.