When Uruguayans go to the polls on Sunday to elect a new president, the results could have lasting impacts on drug policy around the world.

With the country’s landmark marijuana legalization bill last year, Uruguay became the world’s first nation to legalize the production, sale and distribution of marijuana—making it a model for the global legalization movement.

But just ahead of Sunday’s runoff election, polls show that as many as two-thirds of Uruguayans support repealing the marijuana law. Tabare Vasquez of President Jose Mujica’s leftist Frente Amplio (Broad Front) coalition remains well ahead of his challenger, Luis Lacalle Pou of the centre-right Partido Nacional (National Party) in most polls (Spanish), but pro-marijuana legalization advocates are uneasy.

If Lacalle Pou wins, he said in an interview with Reuters last month, he would keep the part of the bill that allows users to grow their own marijuana plants at home (up to six per household) and authorize the so-called social clubs—local non-commercial organizations where up to 45 paying members can jointly cultivate up to 99 plants. But, he said he would ”repeal the rest, in particular the state’s commercialization of the drug.”

What Lacalle Pou was referring to is the licensed sale and distribution of marijuana in pharmacies, where early next year individuals will be able to purchase up to 10 grams of cannabis a week at a government set price of about $1 per gram.

This part of the bill is what distinguishes it from, say, Colorado’s or Washington’s, says Hannah Hetzer, policy manager for the Americas at the Drug Policy Alliance, the largest drug policy reform organization in the United States.

“By selling cannabis in pharmacies at a set price, you are regulating the market that already exists and taking it from the illicit to the licit,” Hetzer tells Quartz.

An unpopular law

Hetzer spent all of 2013 in Uruguay consulting the Regulación Responsable (Responsible Regulation) advocacy campaign as it marketed the marijuana legalization bill to a skeptical Uruguayan public. Though the bill passed in the Broad Front-majority senate, only an estimated 26% (Spanish) of Uruguayans supported it.

The bill’s continued unpopularity, critics say, may explain why Lacalle Pou’s message has resonated in the general public. But it appears that voters view other issues, such as education and security, as more pressing to the national agenda.

“People disagree with the law, but not vehemently,” says Hetzer. “Our research, polling and surveys show that voters are waiting to see how the bill is implemented before they want it repealed.”

Quartz reached out to Uruguay’s National Drug Board, which is in charge of the bill’s implementation, but did not receive comment by press time.

The world is watching

Uruguay’s experiment with marijuana is less than a year old, but its action to break with social norms and combat drug trafficking (Spanish) has inspired its neighbors to re-think drug policy.

In February, the Brazilian senate began debating the legalization (Portuguese) of marijuana for both medical and recreational use. Argentina’s government is currently weighing its options (Spanish) on decriminalizing possession of all illicit drugs, similar to what Portugal did in 2001. In September, the Chilean government approved the country’s first marijuana farm for medical research and development. And, in Ecuador, last month the government freed convicted drug mules in response to a new criminal law that significantly reduced prison time for drug-related offenses.

A Lacalle Pou victory wouldn’t stop that momentum, says Morgan Fox, communications manager for the Marijuana Policy Project, a US organization focused on marijuana policy reform.

“It’s certainly important for these countries to see how Uruguay’s experiment goes,” Fox told Quartz. “But, by doing what it did, the country paved the way for those in the global legalization movement to believe it could happen. That feeling’s not going away.”