A ballot measure to legalize limited possession of marijuana in Colorado continues to lead in the latest Denver Post poll on the question, but it has dropped below 50 percent support.

The poll of 614 likely voters found that 48 percent of respondents support the measure, while 43 percent oppose it. A poll last month found a wider lead for Amendment 64, with 51 percent in support and 40 percent opposed. Both polls have a 4-percentage-point margin of error.

The most noticeable swing in the new poll, taken Tuesday and Wednesday for The Denver Post by SurveyUSA, came among women. The previous poll showed the measure succeeding with women 49 percent to 39 percent. The new poll, however, shows women opposed 48 percent to 40 percent.

Men continue to support the measure, as do young voters and those ages 50 to 64. But a slender lead among voters ages 35 to 49 has turned into a 4-point deficit, while voters 65 and older disapprove of the measure by a wider margin.

The poll comes as the campaigns for and against the measure have been heating up, with both sides announcing a series of endorsements.

Opponents have touted endorsements against the measure from Gov. John Hickenlooper, the Colorado Education Association, the Colorado chapter of the American Academy of Pediatrics and several law-enforcement organizations. On Monday, representatives from the Denver Metro Chamber of Commerce and the Downtown Denver Partnership, along with Denver Mayor Michael Hancock, will speak out against the amendment.

No on 64 spokeswoman Laura Chapin disputed the language of the poll question — which uses the word “decriminalize” — and said the campaign is skeptical of the results.

Neither campaign was shown the results of the latest poll before they were published.

“We have every confidence if people understand what Amendment 64 does … they will vote against amending the Colorado Constitution this way,” she said.

Proponents of the measure, meanwhile, have announced the support of more than 300 doctors in Colorado, the Colorado branch of the NAACP, singer Melissa Etheridge and former Colorado Congressman Tom Tancredo.

In a statement, pro-64 campaign spokeswoman Betty Aldworth said the measure will make Colorado safer.

“Momentum is greater than ever among the volunteers who are working around the state to educate voters, and we look forward to more and more support in these final weeks of the campaign,” Aldworth said.

Amendment 64 would legalize use and possession of up to an ounce of marijuana for people over 21 years old. People would also be allowed to grow up to six marijuana plants in their home.

The measure legalizes marijuana sales at specially regulated retail stores but also allows communities to ban those stores. Public consumption of marijuana would not be allowed.

John Ingold: 303-954-1068, jingold@denverpost.com or twitter.com/john_ingold

About the poll

The survey was taken Tuesday and Wednesday for The Denver Post by SurveyUSA using automated calls to homes and cellphones. Pollsters reached 614 likely voters.