Colorado Gov. John Hickenlooper opposed a 2012 state ballot initiative to allow the sale and use of marijuana for recreational purposes. He told voters it might "increase the number of children using drugs and would detract from efforts to make Colorado the healthiest state in the nation. It sends the wrong message to kids that drugs are OK." Spurning his advice, voters approved it.
So he might be excused if, four years later, he were tempted to gaze upon the results of this experiment and say, "I told you so." In fact, Hickenlooper has done just the opposite. "It's beginning to look like it might work," he said recently.
For years, the state had allowed the medical use of cannabis, which was sold in licensed dispensaries. Under the new system, pot is regulated and taxed much like alcohol. The new shops began doing business Jan. 1, 2014.
Andrew Freedman, the governor's "marijuana czar," acknowledges that "for the most part, Colorado looks a lot like it did before legalization." He says Hickenlooper is "pleasantly surprised that there were not as many challenges as he thought."
The fears expressed back then are familiar ones: Drug use would soar. Kids would take the change as approval to get high. Stoned drivers would make the roads more dangerous. And public health would suffer. But by now, anyone waiting for a parade of horribles may be running out of patience.
There have been some unwelcome side effects. Emergency room visits for marijuana-related problems have increased, apparently because of inexperienced users ingesting too much of the drug -- often in edible form, such as candy bars.
A couple of deaths were blamed on reactions to overdoses. So the state issued new rules to prevent such mistakes.
Aside from those and the emergence of pot tourism, legalization has been remarkable for how unremarkable it's been. Freedman told the Los Angeles Times he's seen no real change in health or safety problems.
The latest edition of "Marijuana Legalization: What Everyone Needs to Know," by researchers Jonathan P. Caulkins, Beau Kilmer and Mark A.R. Kleiman, notes that adult use has risen in Colorado -- though less rapidly than in three other states.
But the authors also say, "It is difficult to know how much of the increase represents real change and how much reflects respondents' increased honesty about their marijuana use." Make certain conduct legal and those engaging in it have less reason to lie.
A federal agency reported in December that Colorado had the nation's highest rate of consumption among kids ages 12 to 17, with nearly 13 percent using it in the previous month. But that rate has been as flat as eastern Colorado. The state Department of Public Safety found "no significant change" in cannabis use by teens.
Blaming the relatively high rate on legalization may get the causation backward. It could be teens smoke a lot of pot because it became legal (for adults, that is). Or it could be that it became legal because people in Colorado smoked a lot of pot.
Alarmists predicted that more people would drive under the influence, causing a surge of highway deaths. But the danger of pot is commonly exaggerated. A study by Eduardo Romano of the Pacific Institute for Research and Evaluation found no evidence that marijuana use by drivers raises their risk of crashing.
"Despite our results, I still think that marijuana contributes to crash risk," he told The New York Times, "only that its contribution is not as important as it was expected." In any event, the state's traffic death rate per 100 million vehicle miles driven actually fell very slightly from 2013 through 2014.
The overall results of legalization have not inspired panic. The Denver Post reports that at least four towns that haven't allowed recreational pot dispensaries are now considering it.
"I think there's enough evidence out there that recreational marijuana can be done safely and responsibly," said Emmett Reistroffer, a member of the Englewood Liquor and Medical Marijuana Licensing Authority. The police chief of Littleton said he wouldn't "anticipate significant negative impact related to crime should the (City) Council choose to allow recreational sales."
Washington, Oregon, Alaska and the District of Columbia have also legalized recreational pot. Voters in California, Nevada and Maine are preparing to decide on their own legalization measures in November.
The question raised by Colorado's mellow experience is not, "Why do it?" It's, "Why not?"