There is a very interesting example at play in the UK today of the difference in strength and influence of different political lobbies. What makes this difference particularly interesting is that it can be seen in the same area of government: public health.
Take three substances and three different approaches: tobacco, alcohol and cannabis.
Tobacco has had a number of measures taken against it in recent years in the name of public health: punitive tax, a ban on smoking in public, a rise in the legal at which to buy and most recently a move towards tobacco going under the counter.
Alcohol gives a different picture. 24 hour licensing liberalised consumption whilst small steps in raising taxation have been taken. There is also discussion of minimum pricing for alcohol, and a strong public discourse against the 'horrors of binge drinking'. There is no hint towards raising the age of consumption or restricting the sale of alcohol any further,
Cannabis remains a banned, Class B drug with penalties for possession.
These substances undoubtedly have a negative impact on health, but arguably this impact is roughly similar for all. Indeed, arguably alcohol has the greatest impact on society - both in terms of health and public order - but also has the least regulation.
Cannabis was briefly reclassified to a Class C drug, but public opinion was strongly against this and it was returned to Class B.
The difference between alcohol and tobacco is that over several years a strong anti-smoking lobby pushed firstly the legal case for a smoking ban (focussing on health and safety for employees) and then developed a discourse which capitalised on public fear of cancer.
Though the health risks of alcohol use have been articulated, current discourse focusses on public order issues. The impact of smoking on health is made clear: it is never good or even neutral. The impact of alcohol on health is less clear, with changing advice about units where many people underestimate their consumption, ocassional research that suggests some alcohol is good for health and the idea that it is only excessive alcohol which is a problem.
Therefore politicians focus on binge drinking and scenes of public disorder. The cost to the NHS is mostly articulated as being in Friday and Saturday night incidents rather than the cumulative effect on health of years of moderate drinking.
It seems that liberalisation of any of these substances is now extremely unlikely. The differing speeds of change are largely explained by the dominance of differing narratives and their ability to persuade public opinion.