Marijuana leaf (Reuters/Anthony Bolante)

Over less than a decade, public opinion has shifted dramatically toward support for the legalization of marijuana. For many years, opinion on the issue was quite stable, but the turn of the millennium unsettled this long-standing consensus: Sentiment in favor of legalization has increased by 20 points in just over a decade. The proportion of Americans who view marijuana use as immoral has fallen from 50 percent to 32 percent in just seven years. A recent national survey showed a narrow national majority in favor of legalization, and its supporters translated this sentiment into ballot initiative victories in Colorado and Washington State in 2012.

These are among the main findings of a paper my Brookings Institution colleague Bill Galston and I published today on the new politics of marijuana. It’s based on a close study of an excellent survey released earlier this year by the Pew Research Center on the People and the Press and also work by Greenberg Quinlan Rosner Research on behalf of groups supporting the legalization of marijuana. You can read the whole paper here.

As we wrote, the structure of public opinion regarding marijuana legalization is distinctive in a number of ways. Among today’s divisive issues, support for marijuana legalization is unusual in cutting across party lines. Generally, broad shifts in cultural attitudes-notably the rise of the 1960s and 1970s counterculture, and then the backlash against it in the 1980s-can trump the influence of party. Gender plays a role, but not necessarily the role one might expect: women are to the “right” of men, more likely to oppose legalization.

Attitudes toward legalization are marked by ambivalence. Many of those who favor legalization do so despite believing that marijuana is harmful or reporting that they feel uncomfortable with its use. Among conservatives, many who believe marijuana should be illegal nonetheless support states’ right to legalize it and take a dim view of government’s ability to enforce a ban.

Among the findings we reported from the Pew survey:

  • Republicans are nearly as likely as Democrats to say they have used marijuana: 43 percent of Republicans reported past use, as did 47 percent of Democrats.
  • Opinion is divided into three age clusters. Americans under 30 are the most strongly supportive of legalization: 64 percent in favor, according to the Pew survey, and 34 percent opposed. Views in the oldest age cohort are, very nearly, exactly reversed: among those over 65, 64 percent oppose legalization, while 33 percent favor it. The middle-aged are more closely split, but have moved toward support for legalization. Among those aged 30 to 49, 55 percent support legalization, while 42 percent are opposed. Those 50 to 64 years old split 53-to-44 percent in favor of legalization.
  • While men favor legalization by 57 percent to 40 percent, women are closely split: 48 percent support legalization, 49 percent oppose it. This finding is closely related to another: while 54 percent of men in the Pew survey report having used marijuana, only 42 percent of women do.
  • There is a strong minority in each party that breaks with its side’s dominant view – which does not happen on public issues as often as it used to. Thus do 37 percent of both conservatives and Republicans favor legalization. Thus do 39 percent of Democrats and 25 percent of liberals oppose it.
  • But even among opponents of legalization, there is substantial skepticism about the value of enforcing laws against marijuana, and also significant support for giving states that legalize it leeway to carry out their experiments.
  • What might be seen as the “states’ rights gap” on enforcing marijuana laws exists for Republicans and conservatives, but not for liberals and Democrats. Asked by Pew if the federal government “should or should not enforce federal marijuana laws” in states that “have decided to allow marijuana use,” 57 percent of Republicans and 52 percent of conservatives said the federal government should not enforce its own prohibitions. The gap among Republicans between the proportion supporting legalization and the proportion who nonetheless want the federal government to stand down in the face of state legalization decisions is 20 percentage points; for conservatives, the figure is 15 percentage points.
  • By contrast, there is the proportion of Democrats who oppose legalization (39 percent) is close to the proportion who favor enforcing federal anti-marijuana laws (35 percent). The two numbers are similar for liberals (25 percent opposing legalization, 26 percent in favor of enforcing federal laws).
  • Overall, 60 percent of Americans think the federal government should not enforce federal marijuana laws in states that legalize it.

And you can find a graphic summarizing the paper here.

As for the future, we conclude by arguing that the lesson of Prohibition in the 1920s and early 1930s is helpful — though, in a sense, in reverse. Prohibition lost public support because of its unintended consequences. The question this time will be whether legalization of marijuana achieves the ends that those who support it promise without an undue number of unanticipated negative side-effects.

The kinds of regulatory regimes states establish will be an important part of the story. How the federal government deals with states that have legalized marijuana will also play a major role in whether these state experiments are seen as successes or failures. This, in turn, will determine whether the strong support for legalization among younger Americans endures and creates a new majority on behalf of a cause once supported by only a few.