The pro-pot movement in California announced a victory this week, as California's Adult Use of Marijuana Act gained 600,000 signatures, far ahead of the 365,000 needed by July 5 to qualify for its November ballot.

On the other side the the country, however, political leaders in liberal Massachusetts, the state that introduced an Obamacare-like system, balk at legalizing marijuana. And Vermont, home of socialist Sen. Bernie Sanders, criticized Massachusetts's marijuana initiative as too lax and killed its own fledgling pot bill.

What's going on here?

While pro-legalization ballot efforts are underway in nine other states, the differences in how political leaders discuss the issue around the country reveals the complexity – and a possible shift – in the debate.

Although backers for the marijuana legalization initiative in California include Lt. Governor and gubernatorial candidate Gavin Newsom and former Facebook President Sean Parker, opposition to the Bay State's initiative reads like a bipartisan who's who of Massachusetts government.

On Wednesday, Gov. Charlie Baker (R), Attorney General Maura Healey (D), and Boston's Mayor Martin Walsh (D) wrote a Boston Globe editorial opposing legalization with a public health argument. They cited Colorado's early experiment with legalization, saying it proved marijuana would be a complex addition to the state:

The costs to our first responders, our medical system, and our cities and towns must be factored in when we speculate about the potential increase in tax revenues from legalizing marijuana. In Colorado, marijuana sales taxes account for just a fraction of one percent of total state revenues. Here in Massachusetts, we face the possibility that any new revenue would be vastly insufficient to cover the cost of ambulance rides, emergency room visits, and treatment.

Massachusetts politicians raised these concerns after seeing the case study for legalization in Colorado, says Sen. Viriato deMacedo (R), one of nine senators who went on a four-day fact-finding mission to Colorado.

"We in the Commonwealth would be better watching and learning from the case study of Colorado for five or six years, rather than just two," he tells The Christian Science Monitor in an interview.

They saw the vast industry opened by legalization, all requiring state-level regulation in everything from pesticide use to the monetary system.

"I think if people understand that this not about – 'Do we want marijuana, yes or no?' – this is about legalizing an entire industry and people competing about who has the best marijuana," Sen. deMacedo says. "It's about money, and I don't think most people have an understanding of that."

He said the logistical challenges of legalization drew concerns from his colleagues in government across the political spectrum. After one year of studied neutrality, the chair of the state's special committee on marijuana Sen. Jason Lewis (D) returned from Colorado with a cautionary tale.

"You're never going to stamp out any of the concerns on accidental ingestion or people not using the product in a responsible way," he told the State House News Service.

The committee was surprised, for example, by the variety of ways consumers ingest marijuana, and by its potency in products. A traditional joint might have 2 percent tetrahydrocannabinol (THC), the drug's active ingredient, but many products now contain as much as 90 percent.

Sen. Lewis told the State House News Service he doubted the state's ability to sufficiently regulate such a complex industry, noting that legalization does not appear to have curbed Colorado's black market for the substance.

"We are also concerned that the effort required at this time to implement marijuana legalization by our state and local governments would consume enormous amounts of time and energy that could otherwise be spent addressing other challenging issues already facing our cities and towns," the state Senate committee members wrote in their report, which was released in early March.

The senators found special concern in the proliferation of marijuana "edibles," which now account for almost half of Colorado's pot sales – and rising. Marijuana-infused products from lollipops to chocolates, which would also be allowed in Massachusetts if voters passed the initiative, induce a delayed "high," leading many consumers to eat them in dangerous quantities.

Vermont has more than echoed that concern. On Tuesday, the state's House of Representatives killed not only a bill to legalize marijuana, a conservative approach Vermont Gov. Peter Shumlin (D) had called "the most careful, deliberate attempt to regulate marijuana in America," but also thwarted any efforts to bring the issue to a referendum, the Associated Press reported.

This move came despite the governor's support, which was based not on a rush toward greater freedom or medical benefits, but because he wanted Vermont's more cautious bill to trump anything Massachusetts decides in November.

"[Vermont's] approach is in stark contrast to the one proposed in the Massachusetts referendum that will be voted on in November, which would allow edibles that have caused huge problems in other states, smoking lounges, home delivery service, and possession of up to 10 ounces of marijuana," Gov. Shumlin wrote. "Vermont's bill allows none of that."

Although the two Northeastern states' governors took slightly different positions on legalization, both cited the opioid epidemic, which has hit the region harder than California or Colorado, for contributing to their cautious approach. Leaders in both states described how they evaluated the costs of introducing another unpredictable drug with an eye toward their already overworked medical community.

"Colorado was in a position where they had no case study, and I think a lot of them didn't think it was going to pass and they didn’t really plan for it," deMacedo says. "They've had to tweak [the bill multiple] times because of some significant concerns."

November elections will show how new arguments born of fresh experience and observation – rather than the free-market arguments for job creation more commonly employed in the West – impact voters. Initiatives could appear on ballots in Florida, Ohio, Arkansas, Missouri, Maine, Nevada, Arizona, and Michigan.

Nationwide, momentum appears to be building toward legalization, with polls showing majority support for legal marijuana. Advocates have succeed in eroding much of its traditional stigma, according to Tom Angell, chairman of Marijuana Majority and a legalization advocate of 15 years.

"Previously when I told people what I do for a living, people would laugh at me, say that's never going to happen," Mr. Angell tells the Monitor. "Now politicians are knocking on our doors and wanting to introduce bills and amendments, and there’s this industry that's emerging."

Or is it? Voters still profess unusual ambivalence about the issue, as William A. Galston and E.J. Dionne Jr. wrote in a study for the Brookings Institution.

"Conservatives are, among the ideological groups, the strongest opponents of legalization. Yet their traditional sympathy for states’ rights and their skepticism about government efficacy weakens their support for strong enforcement of anti-marijuana laws," the researchers wrote.

Marijuana legalization may now prove immune to the partisan debate otherwise rampant in political life, but long-term, it has followed national politics' changing trajectories to a surprising degree. Support for marijuana rose for the first time during the counterculture movement of 1960s and fell during the conservative backlash of the next two decades, according to Pew Research Center. The next spike of support began in the early 1990s, as Bill Clinton took office, and plateaued throughout the Bush administration.

The current momentum that has inspired a spate of state initiatives began in 2008, Angell says. He cited the economic downturn for increasing the public's interest in turning drugs into job creation, but also suggested that President Obama played a direct role.

"He is someone who said, 'Yeah, I used marijuana. It’s no big deal,'" Angell said. "With him coming in, there’s a sense that, 'This is possible.'"

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Public opinion numbers back the claim, as 2008 marks the beginning of a steep rise in support of legalization from 32 percent to 53 percent currently, according to Pew.

The examples of Vermont and Massachusetts suggest that there are crosscurrents in this trend, however.