Americans show large levels of support for the legalization of marijuana, with 58% of Americans overall (and 71% of 18 to 34-year-olds) believing that people should be able to consume cannabis without sanctions, according to a new Gallup poll.

While young people, independents and Democrats show the most robust support for legalization, liberal attitudes are also gaining ground in the older population -- the only age group against legalization, according to the poll. While only 4% of people 65 and older supported legalization in 1969, 35% of people in that age group support legalization in 2015, "a function of attitude change within generations of Americans over the course of their adult life spans," and new generations of older adults with more progressive beliefs, said Gallup.

The survey bolsters the case that "no other law is enforced so harshly and pervasively yet deemed unnecessary by so many Americans," Ethan Nadelmann, executive director of the Drug Policy Alliance said in a statement. In 2014 almost 701,000 people were arrested for marijuana, with blacks four times as likely to be arrested as whites, according to the Alliance. "More elected officials need to realize that legalizing marijuana is not just the right thing to do: It's the politically smart thing to do," Nadelmann said.

Gallup noted that while federal law still prohibits marijuana use, four states and the Washington D.C. have legalized weed and Ohio voters will decide a ballot initiative on the topic this election day.