Before anybody starts celebrating victories or emerges on socio-psychological analysis of "Germans", let's put this poll into context. I haven't found a documentation on the exact question that has been polled, but press reports suggest that it was along the lines of "Do you support complete legalisation of Marihuana or not"?
There had been a more
differentiated poll in 2010, which provided the following options for answering:
Maintain or even tighten the (rather liberal) regulation: 40%
Maintain formal prohibition, but de-criminalise usage: 30%
Completely legalise possession (but not trade): 5%
Legalise it similar to alcohol (taxation, sale only to adults, etc.): 19%
No opinion: 7%
If we take options 3 & 4 as more-less corresponding to the legalisation option given in the recent FORSA poll, the support for complete legalisation has gone up from 24% in 2010 to 29% in 2013.
It is also worth noting that, unlike the US, the issue isn't discussed much on the political level. Most importantly, no politician has so far presented an estimate of the additional tax revenue, and the reduction in prosecution cost, that could be obtained by legalisation similar to alcohol. We should be easily talking about 1-2 bn € p.a. here. Once such figures enter the public debate, knowing my fiscally sensitive fellow countrymen, I am quite sure the opinion would change substantially towards liberalisation & taxation.
Oh, did I say the issue isn't discussed much politically? Well, there is one exception - Berln's CDU Senator of Interior in 2012 came out with a proposal to reduce the amount below which possession of Cannabis is tolerated from 15 grams to 6 grams. FORSA, the same pollster that did the current poll, in June 2012 polled
Berlin citizens' opinion on that proposal: 47% supported less tolerance, 51% were in favour of Berlin's current liberal regulation or wanted even more liberalisation. 34% of respondents had already consumed Cannabis. There is also an interesting East-West split, with people in East Berlin having less consumption experience (27% vs. 38% West), and in majority favouring stronger prosecution.