Justin Trudeau's support for the legalization of marijuana and his admission that he has smoked it as recently as three years ago is not without controversy, but the Liberal Leader appears to be on the right side of public opinion.

That opinion has been increasingly growing from opposition to acceptance, with support for decriminalization and legalization claiming a majority of Canadians in the last decade. That support cuts across regional, generational and political boundaries. Though less supportive than others, even older Canadians and Conservatives are on board with reform of marijuana laws.

Evolution of pot support

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Tolerance of marijuana was significantly lower in the past. A poll by Gallup in 1970 found that only 41 per cent of Canadians supported giving fines, but no sentences, for possession of marijuana, while 45 per cent were opposed. In 1977, an Environics poll showed that only 19 per cent of Canadians were in support of full legalization, compared to 77 per cent who were opposed.

But by the 1990s, a slim majority of Canadians disagreed that marijuana possession should still be a criminal offense in an Angus-Reid poll, while the proportion who told Environics they supported legalization had increased to 29 per cent in 1995.

By the mid-2000s, support for either decriminalization or legalization reached a majority of Canadians. While 45 per cent – a plurality, but not a majority, of respondents – supported decriminalization in an EKOS poll of June 2000, that had increased to 50 per cent by 2010 and 66 per cent in the most recent poll conducted by Ipsos-Reid on the issue, in June 2012. Support for legalization was as high as 55 per cent in a 2007 poll by Angus-Reid, and has wobbled back and forth since then. Angus-Reid found support for legalization to be at 50 per cent in November 2010, for example, and 57 per cent in November 2012. Only 39 per cent opposed legalization in that poll, the most recent one asking explicitly about legalization.

Overwhelming approval today

But when given a choice between legalization and decriminalization, opinion is split. A poll conducted last week by Forum Research found that 36 per cent of Canadians preferred legalization, while 34 per cent were in favour of decriminalization. Another 15 per cent felt the laws should be kept as is (a proportion that has been shrinking over the last two years), and 13 per cent felt the laws should be harsher. Nevertheless, a relaxing of the rules concerning marijuana is overwhelmingly favoured: 70 per cent said they wanted legalization or decriminalization.

It should be noted that Canadians do see a difference between marijuana and other illegal drugs. Angus-Reid has consistently found that, while legalization has met the support of a majority of Canadians, support for the legalization of other drugs such as cocaine, ecstasy, heroin, and meth has only registered around 10 per cent or less. In other words, support for legalizing marijuana is not some libertarian position in favour of less government intrusion, but specifically about this particular drug.

The (lack of a) generation gap

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And, contrary to popular opinion, the Liberal leader's move should not necessarily be seen as a means of capturing the youth vote. The polls do not always show that the youngest Canadians are the most likely to support legalization. In fact, it seems that the only generation gap is between seniors and the rest of the population.

The survey by Ipsos-Reid in June 2012 on decriminalization found support to be highest among middle-aged Canadians between the ages of 35 and 54 (69 per cent), while it stood at 68 per cent among those 34 or younger. Support was still high among the oldest Canadians, at 62 per cent, but that was the only generational gap. The results of Angus-Reid's November 2012 poll on legalization were similar: 58 per cent support among 18-to-34 year olds, 61 per cent among those between the ages of 35 and 54, and only 51 per cent among those 55 or older. That has been a consistent trend: the Angus-Reid poll of 2007 found a similar distribution.

The polling by Forum has been less consistent on this issue with no obvious correlation between age and support for either legalization or decriminalization, though in their last two surveys support for legalization was highest among the young. On the other hand, they have also shown that the most significant increase in support for some relaxing of the laws has come among the oldest Canadians.

In any case, if there does seem to be some sort of generational gap it could be between those who were teenagers before and after, say, the benchmark year of 1968. That broadly aligns with the most important difference recorded by Ipsos-Reid and Angus-Reid between Canadians over and under the age of 55. Even so, the consensus among older Canadians is still for legalization or decriminalization.

Not divided on party lines

Politically, the move could pay dividends for the Liberal leader. Support for either legalization or decriminalization cuts across party lines, with Liberals and New Democrats almost evenly split between support for either options. But the Conservatives, offside with public opinion generally, seem to be on the wrong path with their own supporters: 62 per cent of them told Forum they favoured either legalization or decriminalization.

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Furthermore, support for legalization has consistently been highest in British Columbia. The province is setting up to be a major battleground in 2015, and the Liberals appear to be on the right side of the issue there. Nationwide, it seems that the Liberals have not taken much of a risk in moving so strongly on changes to how the law handles marijuana. If the Tories and NDP are to use Mr. Trudeau's position against him, they will first have to transform how Canadians feel about the drug itself.

Éric Grenier writes about politics and polls at ThreeHundredEight.com .