Proposition C would only go into effect if it passes and the two amendments fail. If both constitutional amendments win, the one with the most votes takes effect.

The Missouri Medical Cannabis Trade Association sprouted in recent months to influence and guide policymakers, entrepreneurs, doctors and lawyers.

The group’s leadership says it has no official ties with any of the three measures but is endorsing Amendment 2, said John Curtis, the co-chairman of the association.

“This is not going to be the kind of thing where you have a retail store on every corner because there’s no regulation and people just do what they want,” Curtis said. “This is a tightly controlled enterprise that’s really dictated by the state. Amendment 2 is quite well-written in our opinion.”

Viets’ confidence heading into Election Day was bolstered by polling showing that Americans’ attitudes toward the drug have shifted dramatically in recent years.

According to a Pew Research Center survey released this month, 62 percent of Americans think the government should legalize marijuana outright, not just for medical use.