For years polls have shown that a majority of people in the U.S. believe in legalizing marijuana. This is especially evident on the left, with 73% of self-identified “liberals” supporting legalization in a 2014 poll. So why has only one current Democratic governor—Vermont’s Peter Shumlin—indicated that they are open to the idea of legalizing recreational pot?

The Democratic Governors Association (DGA), a tax-exempt 527 political organization that finances campaigns and advertisements in support of Democratic gubernatorial candidates, has taken more than $18 million from pharmaceutical industry interests over the past ten years, according to data from the Center for Responsive Politics. In recent years, the industry has accelerated its giving to the DGA, with only labor interests giving more to the organization over the last two election cycles.

Marijuana has been shown in studies to be good medicine for a range of ailments, including multiple sclerosis, glaucoma, and cancer — which means that pharmaceutical companies have a strong financial incentive to keep it illegal. If people could easily grow or purchase natural alternatives to habit-forming, synthetic pharmaceuticals, companies that produce pain killers and other pills could suffer big profit losses. Instead, the pharmaceutical industry intends to make money on the medicinal qualities of marijuana by winning federal approval for drugs that are made from derivative byproducts while lobbying to keep the natural plant, which is generally more effective, illegal.

The movement to legalize marijuana has been waged in large part at the state level, with four states (Alaska, Colorado, Oregon, and Washington) having approved legalization in recent years through popular ballot measures. Twenty-three states have legalized medical marijuana (a few of those are still working out the final details), and 17 have passed decriminalization laws.

But even in the states that have approved full legalization, the Democratic governors there have stood out in opposition.

Colorado’s Democratic governor, John Hickenlooper, recently said that he thinks the state’s decision to legalize pot in 2012 was a mistake.

“If I could’ve waved a wand the day after the election, I would’ve reversed the election and said, ‘This was a bad idea,'” Hickenlooper explained during an appearance on CNBC on January 23, 2015. “You don’t want to be the first person to do something like this.”

The DGA spent nearly $4.9 million on ads in support of Hickenlooper in his 2014 re-election bid. They donated another $2.4 million to Making Colorado Great, a 527 that ran ads against Hickenlooper’s Republican opponent.

The only sitting Democratic governor who has signaled an openness to legalizing marijuana is Vermont’s Peter Shumlin. Vermont is currently experiencing a major public health crisis, with a shocking 770 percent increase in the number of people being treated for heroin addiction since 2000. The heroin epidemic in Vermont has been blamed on over-prescription of addictive painkillers like OxyContin and Vicodin. Given the severity of the heroin crisis in his state, Shumlin’s moves towards legalizing marijuana as an antidote seem like the least he could do. All three Republican primary candidates in the 2014 Vermont gubernatorial race said that they support marijuana legalization, so Shumlin’s position is clearly not considered progressive in the state.

Even in the most liberal states in America, Democratic governors have been reserved on legalization. In New York, Governor Andrew Cuomo supported legislation that legalizes medical marijuana in processed forms like pills, oils, and tinctures. Smoking the plant is still illegal. In California, which legalized medical marijuana in 1996, Democratic Governor Jerry Brown thinks full legalization could make the state less competitive. “The world's pretty dangerous, very competitive,” Brown said on Meet the Press in March, 2014. “I think we need to stay alert, if not 24 hours a day, more than some of the potheads might be able to put together."

Below is a look at the top 10 pharmaceutical interest donors to the Democratic Governors Association, from 1/1/2005 - 12/31/2014:

Pfizer $3,063,990

AstraZeneca $2,330,798

PhRMA $2,126,408

GlaxoSmithKline $2,034,367

Amgen $1,165,175

Eli Lilly and Co $991,177

Allergan $933,420

Merck Co $827,680

Sanofi Aventis $685,976

Novo Nordisk $669,450