Amendment 64, which would legalize marijuana for adults over the age of 21 in Colorado, has an eleven point lead according to a new SurveyUSA poll of likely voters conducted for the Denver Post:

The poll found that the measure, Amendment 64, has the support of 51 percent of likely voters surveyed, compared with 40 percent opposed. Men favor the measure more than women, a common gender split on the issue. But 49 percent of women polled said they support the measure, compared with 39 percent who said they are opposed.

Across every income bracket and in every age group except those 65 and older, more voters told pollsters they support the measure than oppose it, though some of the leads fall within the 4-percentage-point margin of error. Voters younger than 35 support the measure by a margin of 30 percentage points, 61 percent to 31 percent, according to the poll.

The good news for the campaign is that it has a decent lead and it is currently over the all-important 50 percent mark. If the initiative can simply maintain its current level of support it would narrowly win approval and become law in the Colorado.

The bad news for the campaign is that ballot initiatives tend to lose some support as the election nears. Undecided voters tend to break against initiatives. Holding on to an eleven point lead is an achievable but difficult task for a ballot measure.

All indications are that the final results are going to be very close. Amendment 64 will probably either narrowly win or lose by just a few percentage points. The relative turnout of different age groups could easily make the difference.