The momentum toward marijuana legalization — already accelerated this year by a raft of state ballot measures — could get an even bigger boost if Democrats win control of the Senate.

That’s partly because the controlling party will choose the chairman of the committee that determines whether a sweeping marijuana proposal advances or dies.

The so-called CARERS Act has stalled in the Judiciary Committee under Chairman Charles E. Grassley of Iowa, who, in the past, has staunchly opposed legalized marijuana.

The Democrat next in line to take the gavel, Patrick J. Leahy, has shown more interest. He said in 2013 that federal officials should not “waste their time” prosecuting marijuana crimes in states where it is legal. He also comes from Vermont, which has led the country in legalization efforts.

Michael Collins, deputy director of national affairs at the Drug Policy Alliance, a pro-legalization group, called Grassley’s reticence to take on marijuana-related measures an “obstacle” to legalization.

“If Sen. Leahy takes the gavel, we are a little more optimistic,” he said.

Democrats need to pick up a net of five seats next year — four if they win the White House — to control the Senate. They appear more likely than not to accomplish that feat, even after the presidential race was jolted last week by FBI Director James B. Comey’s announcement that the bureau is investigating newly unearthed emails possibly related to Hillary Clinton’s use of a private server while she was secretary of State. 

Polls this week showed Clinton’s lead over Republican nominee Donald Trump was virtually unchanged. And according to The Rothenberg & Gonzales Political Report/Roll Call, Democrats are still more likely than not to win control of the Senate, but the most competitive races are close enough that a subtle shift could have a significant impact. 

Hitting a wall

When the CARERS Act was introduced in March 2015, it was considered historically significant. Most key marijuana-related votes had taken place on the House side, through incremental changes tucked into unrelated bills.

But here was the Senate, proposing one of the most comprehensive pot-related bills ever. CARERS focused on medical use — considered an easier sell. But it tackled many of legalization advocates’ biggest issues.

The bill would make it easier to research the medical benefits of cannabis and to buy and sell medical marijuana in the growing number of states where it is legal. It would also make it easier for veterans to access medical marijuana.

Its original sponsors indicated a promising bipartisan appeal: Republican libertarian firebrand Rand Paul of Kentucky, and Democrats Kirsten Gillibrand of New York and Cory Booker, of New Jersey.

And it quickly attracted a list of co-sponsors from both sides of the aisle — including Charles E. Schumer of New York, a future shoe-in for majority leader under the Democrats, and Lindsey Graham, a conservative senior senator from South Carolina.

But the bill first had to pass through Grassley, who has linked lax marijuana laws and enforcement to the epidemic of opioid and heroin use.

Grassley has held two marijuana-related hearings, one on researching its medical benefits, and another on cannabidiol, a component of marijuana that is thought to ease symptoms of epilepsy. The CARERS Act would remove cannabidiol, or CBD, from the Controlled Substances Act, facilitating research and patient access. Grassley expressed support for that part of the measure, but he made it clear that his interest is limited to medical potential.

“Legitimate, medical research shouldn’t be confused at all with smoking marijuana for recreational purposes, which the science tells us can be harmful and addictive, especially for young people,” he said at a July hearing.

Grassley supports research into medical marijuana and its constituent parts, but opposes other parts of the bill, according to spokeswoman Jill Gerber. She pointed out that few Judiciary Committee members had co-sponsored the bill, an indication, she said, that there might not be enough support to pass it even if Grassley scheduled a vote.

Indeed, some of the other committee members, including Democrat Dianne Feinstein of California, and Republican Jeff Sessions of Alabama, have been outspoken in their opposition to legalization. (Sessions said in April that “good people don’t smoke marijuana.”)

But advocates have been tallying the potential votes on their side and are coming up with a different conclusion. CARERS co-sponsors Graham and Schumer sit on the Judiciary committee and others have made statements that indicate they could be persuaded, the Drug Policy Alliance’s Collins said.

“This is not something that Leahy would have to shove down representatives’ throats and then they would have a knock-down, drag-out fight on the floor,” he said.

Legalization advocates viewed the marijuana hearings as a sign that Grassley had softened his position. But they said the bill’s prospects would be better under Leahy. They noted that the Vermont senator showed support for states that have legalized marijuana when he chaired the committee the last time Democrats controlled the Senate. Leahy held a hearing on drug policy in 2013, saying state laws legalizing marijuana “should be respected.”

Leahy did not respond to a request to comment for this story.

Shifting attitudes

The CARERS Act sponsors expect to reintroduce the bill in the next Congress and were optimistic about its chances, according to a Democratic staffer with knowledge of the bill.

“Attitudes about medical marijuana are shifting quickly,” Booker said in a statement. “Election Day could represent another big step forward. I expect the momentum behind the CARERS Act to grow.”

A companion bill introduced on the House side has 42 co-sponsors, including 14 Republicans. Advocates say it has a good chance of passing even if Republicans maintain control of the House, which most projections indicate is the most likely outcome in November.

Other marijuana-related legislation has passed with increasing bipartisan support every year since 2014, when the House adopted an amendment to an appropriations bill prohibiting the use of federal money to enforce marijuana laws in states that have legalized it for medical use.

Legalization advocates are also optimistic that the Democrats next in line to head the Banking and Finance committees would help advance bills aimed at easing financial restrictions on pot-related businesses. Both are front-line issues in the legalization movement that are also addressed in the CARERS Act.

Federal laws make it difficult for businesses that sell marijuana to get loans or open bank accounts, forcing them to do most of their transactions in cash. They are also prohibited from taking tax deductions for their expenses.

The Obama administration tried to reassure banks in 2014 that they would not be prosecuted for working with legal businesses. But it did not grant them immunity to  prosecution and civil penalties. Though some banks have found ways to work around federal restrictions, the majority still avoid the industry.

Ohio Sen. Sherrod Brown, the Banking Committee’s top Democrat, has expressed reservations on marijuana-related issues in the past, but he said last year that he supported legalized medical marijuana. (Ohio legalized medical marijuana in September.)

And Sen. Ron Wyden of Oregon, the ranking Democrat on the Finance Committee, sponsored bills this term that would make it easier for marijuana-related businesses to advertise and to take tax deductions.

A turning point?

But that’s not the only reason marijuana advocates are calling the 2016 election a pivotal one.  

“For those of us who are crusading [for] the end of this failed prohibition of marijuana, this could well be the turning point,” said Oregon Democratic Rep. Earl Blumenauer, who was campaigning in Arizona for that state’s marijuana ballot measure.

Dozens of marijuana-related bills in the House and Senate could get a better reception in the coming Congress, regardless of which party controls the Senate and House, advocates say.

Five states, including the political bellwether of California, will vote to allow adult recreational use, potentially bringing to nine the total of states with full legalization plus the District of Columbia, and potentially bringing the percentage of Americans living in states where pot use is legal to as much as 25 percent from 5 percent.

An additional four states will consider medical use this election. At present, more than two dozen states allow it. A Gallup poll released this month showed a record high of 60 percent of Americans support marijuana legalization.

“What happens with these nine states on the 8th could propel a breakthrough in Congress and its going to be a huge signal to the other folks around the country,” Blumenauer said.

Taylor West, deputy director of the National Cannabis Industry Association, had a similar interpretation.

“The reality is, after Nov. 8, there is going to be a significantly larger number of members of Congress who have constituents who are affected by the way the [federal] government approaches cannabis policy,” she said.