Meanwhile, support for the legalization of marijuana for recreational use is taking off. Forty-eight percent now back it, with 41 percent opposed.

The survey finds a once-large margin of support for casinos has all but evaporated in recent weeks, with 46 percent now in support of casinos and 43 percent opposed.

Public opinion on casinos and marijuana legalization is rapidly shifting in Massachusetts, according to a new WBUR poll.

"There's much more volatility than I recall seeing in terms of some big social issues."

Steve Koczela, president of the MassINC Polling Group, which conducted the WBUR poll (topline, crosstabs), says the quick changes on casinos and marijuana are akin to the rapid shift in public opinion on gay marriage nationwide.

"There's much more volatility than I recall seeing in terms of some big social issues," he said.

The WBUR poll of 500 likely voters conducted between March 14 and 16 comes as advocates eye ballot measures on both issues.

Marijuana legalization advocates are pushing for a 2016 referendum. And gambling opponents are hoping to get a measure on the ballot this fall that would repeal the state's casino law.

Attorney General Martha Coakley has ruled the casino measure unconstitutional. But activists are appealing that ruling in court. And Kathleen Conley Norbut, a former Monson selectman active in the statewide opposition to casinos, says shifting public opinion on the issue is encouraging.

"We're doing this because we're going to win," she said. "We don't have the deep pockets. What we have is a commitment to our communities, to our democracy and to see that the commonwealth of Massachusetts does the right thing."

Casino Support Softens

Mohegan Sun, vying for a casino at the Suffolk Downs racetrack in Revere, declined comment on the poll. Wynn Resorts, competing with Mohegan Sun for the sole Boston-area casino license, did not respond to requests for comment.

There has been plenty of local opposition to casinos. Voters in West Springfield, East Boston, Palmer and Milford shot down pricey gambling resort proposals last year. But statewide support for casinos held strong through 2013.

A November poll from the Western New England University Polling Institute showed voters statewide supported casinos by a 60-33 margin.

A January WBUR poll suggested a softening of that support. And the new WBUR survey shows a more dramatic shift; the three-point gap between supporters and opponents is within the poll's margin of error of 4.4 percent.

Koczela said it's difficult to say why public opinion is changing on casinos. But he pointed to a string of unflattering stories about the companies vying for one of three casino licenses — and the state regulators reviewing their bids.

"There's been a lot of headlines about, sort of, the underside of this issue and nothing really positive to show for it yet," he said. "No voter has gone to a concert or used a slot machine or sat down at a blackjack table yet."

Whatever the impact of the headlines, follow-up interviews with poll respondents suggest that for some voters bedrock concerns about the impact on poor people — and on broader communities — are a factor.

"People who can't afford it throw a lot of money in it," said retired Acton caterer Joan Appleton. "I also think it lowers property values around. And I just don't think they're good."

David Davignon, a civil engineer from Acushnet, acknowledged some concern about gambling addiction. But he said Massachusetts should not stand by while local dollars flow to the Foxwoods and Mohegan Sun casinos in Connecticut.

"All the money that, you know, two casinos make in Connecticut from Massachusetts residents — you know, if we could take some of that and put it into our own budget it would help," he said.

Increased Support For Marijuana Legalization

Massachusetts voters decriminalized possession of small amounts of pot in 2008 and approved medical marijuana in 2012. But local and national advocates want Massachusetts to join Colorado and Washington state in legalizing recreational use of the drug.

As recently as November, a Western New England University Polling Institute survey suggested a tough climb: 52 percent of voters in the poll were opposed to legalization and 39 percent in favor.

But those numbers appear to have flipped in recent months. A Boston Herald/Suffolk University poll last month suggested a big shift on legalization, showing majority support for the first time. The WBUR poll confirms the trend.

Young voters support legalization by substantial margins. And because they tend to turn out in larger numbers in presidential years, advocates are aiming to put the measure on the ballot in two years.

They say the state will be a major focus in what they view as a pivotal year for marijuana law reform nationwide.

"Massachusetts is definitely in the top tier of reform states in 2016," said Allen St. Pierre, executive director of NORML, the National Organization for the Reform of Marijuana Laws. "We speculate strongly it will be joining California and Maine as two states where voters will be asked to cast votes to legalize marijuana. In all three states, polling is very supportive."

(Pew Research Center chart, from April 2013)

Massachusetts law enforcement has already come out in opposition to the legalization push, arguing that it will send the wrong message to children.

The change in Massachusetts opinion on the issue is emblematic of a national shift. For the first time last year, a majority of Americans said they support legalizing marijuana.

The evolving views of Baby Boomers have been a critical factor in the emergence of a pro-pot majority.

"Thirty or 40 years ago, when they were young, they supported [legalization]," Koczela said of Boomers. "And then as they became parents and as they went through their careers, they opposed it. And now you're seeing them come back actually to support it again."

Poll respondent Janice Ekstrand, 65, of Fall River is among the Boomers who have changed their minds.

Ekstrand, a retired receptionist, said she never would have supported legalization a decade ago. But her views have changed as she's watched marijuana use become more prevalent — and seen more people go to prison

"There are so many people in jail for small infractions of the law," she said.

-- Here are the poll's topline results (via Scribd):

-- Here are the poll's crosstabs (via Scribd):