Nearly two-thirds of Americans say smoking marijuana is “morally acceptable,” while 31 percent disapprove of pot on moral grounds, according to a survey released Monday by Gallup.

That’s a sharp jump from 2013, when a similarly worded question in a Public Religion Research Institute survey found that slightly fewer than half of Americans said it was morally acceptable to smoke marijuana.

The shift in moral acceptance of marijuana mirrors the shift in support for legalization over that time period, which rose from 48 percent at the end of 2012 to 64 percent last fall, according to Gallup.

On the spectrum of morality, Americans now rate marijuana use similarly to gay and lesbian relations, stem cell research or having a baby outside of marriage, according to Gallup. It’s seen as significantly more acceptable than medical testing on animals, abortion or pornography. But it’s viewed as less acceptable than alcohol use, which 78 percent of respondents say is morally acceptable.

The gap in the acceptance of marijuana and alcohol is driven almost entirely by conservatives, the Gallup data shows. Marijuana and alcohol use are viewed as morally acceptable by large majorities of self-described liberals and moderates — who together comprise about 61 percent of the adult population. Among conservatives, however, 75 percent say drinking is acceptable, while 47 percent say the same of marijuana use.

While marijuana legalization has enjoyed majority support from Democratic voters since at least 2010, many leading Democratic politicians have been slow to embrace the issue. But there are signs that’s starting to change: Earlier this year Senate Minority Leader Charles E. Schumer, D-N.Y., introduced a bill in the Senate that would decriminalize marijuana use at the federal level.

The Marijuana Justice Act, another Senate bill that would legalize marijuana nationwide and penalize states that refused to do so, has attracted a number of leading Democrats as co-sponsors, including Sens. Cory Booker (N.J.), Kirsten Gillibrand (N.Y.) and Kamala D. Harris (Calif.), and independent Sen. Bernie Sanders (Vt.).

In November, Michigan voters will decide whether to legalize the drug and voters in Utah and Missouri will consider medical marijuana measures.