Colorado Gov. John Hickenlooper says his state's voters were "reckless" for voting to become the first state to legalize marijuana for recreational use. The Democrat's statement came during a debate Monday with his Republican opponent, Bob Beauprez, just four weeks before voters head to the polls for the state's hotly contested gubernatorial election.

In 2012, more than 55 percent of voters in Colorado supported Amendment 64, which legalized marijuana for recreational use. The amendment aimed to regulate marijuana in roughly the same way alcohol is regulated.

Since the new law took effect in 2014, the state is on track to raise more than $40 million in new annual revenues for education and other priorities from marijuana-related taxes. There has been little evidence that crime rates or driving fatalities have increased since the law took effect. In fact, the opposite appears to be true: Violent crime rates in Denver were lower in the first half of 2014, and traffic fatalities in the state are near a record low.

Hickenlooper was asked at Monday's Denver Metro Chamber of Commerce debate what he would tell other states considering legalizing marijuana.

"Any governor that looks at doing this before we see what the consequences are, I would view it as reckless," he said.

Asked if he thought voters in Colorado were reckless for legalizing marijuana, Hickenlooper responded: "I think for us to do that without having all the data, there is not enough data, and to a certain extent you could say it was reckless. I'm not saying it was reckless because I'll get quoted everywhere, but if it was up to me I wouldn't have done it, right. I opposed it from the very beginning. In matter of fact, all right, what the hell -- I'll say it was reckless."

Hickenlooper said he is concerned that teenagers using the drug may experience long-term-memory loss. The governor, who made his fortune as a beer brewer, did not express similar criticisms or concerns about alcohol, which many scientists consider far more toxic than marijuana.

Polls show Hickenlooper locked in a tough re-election campaign against Beauprez, a bank executive and former congressman. Beauprez has previously said he opposes marijuana legalization.

This story has been updated to reflect more recent projections of marijuana-related sales tax revenue.