Voters in Florida approved the medical use of marijuana Tuesday, while voters in California were expected to vote for a ballot initiative legalizing the recreational use of the drug.
Partial returns showed voters in Maine and Massachusetts also leaning toward approving recreational marijuana use by adults. Arizona voters are considering a similar measure.
In Arkansas, a medical marijuana measure was passing by a slim margin in early returns. North Dakota and Montana also are voting on ballot questions that would allow the medical use of the drug.
Gun-control and death-penalty questions were on ballots in several states Tuesday, along with proposals to increase the minimum wage. In Colorado, voters faced a proposal to provide universal health care to residents of the state.
Before Tuesday, medical marijuana was legal in more than half of the 50 states, with recreational use permitted in four – Alaska, Colorado, Oregon and Washington – as well as in the District of Columbia. If all the marijuana initiatives are approved, more than 23 percent of the U.S. population will live in states where recreational marijuana is legal, according to The Associated Press.
"We're fast approaching the day when Americans will look back on the marijuana wars of recent decades the same way we now look back on alcohol prohibition: as a costly, foolish and deadly mistake," said Ethan Nadelmann, executive director of the Drug Policy Alliance, which pushes for national legalization.
The votes to expand the use of marijuana come just days after President Barack Obama acknowledged in an interview with comedian and activist Bill Maher his growing concern about the conflict between state and federal laws.
"The Justice Department, DEA, FBI – for them to try to straddle and try to figure out how they're supposed to enforce some laws in some places and not in others, that is not going to be tenable," Obama said.
Democratic presidential nominee Hillary Clinton has said she supports decriminalizing marijuana. National polls show that a majority of Americans support the drug's legalization.
Republican nominee Donald Trump's position is less clear. Although he has previously said he supports decriminalization, he has been vague during the campaign.
Nadelmann said what concerns him more are some of the Trump supporters the nominee has mentioned as possible Cabinet members, including New Jersey Gov. Chris Christie and former New York mayor Rudolph Giuliani. Nadelmann described both as "drug warriors."
The measures also faced strong opposition from corners such as law enforcement groups and religious leaders. In California, small independent growers cited concerns about being squeezed out by big corporate farms.
Colorado voters, who two years ago voted in favor of recreational marijuana, were not as receptive to a proposal to provide universal health care, polls showed.
The proposed health-care initiative would replace private and employer-provided insurance, and it called for a 10 percent payroll tax to support the plan. Vermont Sen. Bernie Sanders, an independent who made universal health care a key issue in his campaign for the Democratic presidential nomination, visited Colorado to stump for the initiative.
Proponents of the initiative said it would provide coverage to more than 350,000 uninsured Colorado residents, as well as lower costs for residents now paying high premiums and deductibles. Opponents said the measure was too costly, with a price tag of $36 billion.
Colorado voters were also considering a proposition to legalize assisted suicide there, now allowed in six states.
Increasing pay for low-wage workers also has gained popularity with the public in recent years, and initiatives to gradually raise the minimum wage to $12 were under consideration in Colorado, Arizona and Maine. Voters in Washington state were considering a proposal to raise the minimum wage, now $9.47 an hour, to $13.50 hourly by 2020. The federal minimum wage is $7.25 an hour.
Proposals to require background checks on nearly all gun sales were on the ballot in Maine and Nevada, states where a group founded by former New York City mayor Michael Bloomberg spent millions promoting the measures. Supporters say the changes would close the "gun-show loophole" that allows felons and people with mental illnesses to avoid background checks by buying firearms online and from private sellers.
California Gov. Jerry Brown, a Democrat, is asking voters to back an initiative to help reduce the state's unwieldy prison population. The measure would offer parole for nonviolent criminals, as well as remove prosecutors' authority to decide whether to try juveniles as adults, giving it instead to judges. Opponents warned that the measure could result in violent criminals being let loose. A separate ballot initiative would abolish the death penalty in the state.
Californians were also considering a ballot initiative to give state-funded insurance plans the same discount on prescription drugs that is offered to patients covered by the Department of Veterans Affairs. Pharmaceutical companies campaigned heavily against the measure, while Sanders campaigned for it.
Meanwhile voters in Nebraska were asked to decide whether to reinstate the death penalty, which the state legislature abolished last year.