Miguel Azucena carries a stack of forms with signatures as staffers with the DC Cannabis Campaign keep track of local voters who added their support to legalize marijuana, on June 26. (Nikki Kahn/The Washington Post)

Voters in the District of Columbia are poised to follow Colorado and Washington state into a closely watched experiment to legalize marijuana, according to a new NBC4/Washington Post/Marist poll.

By an almost 2-to-1 margin, likely voters in the city’s Nov. 4 election say they support Initiative 71, a ballot measure that would legalize possession, home cultivation and the sale of paraphernalia to smoke marijuana in the nation’s capital.

The results show an electorate unshaken — even emboldened — nine months after legal marijuana sales began in Colorado and six months after D.C. lawmakers stripped away jail time for possession, making it just a $25 offense.

Although the District has so far felt little fallout from those moves, full legalization on the streets surrounding the White House would thrust the District into an untenable conflict with federal drug laws, potentially hastening the arrival of a larger national debate. It would also complicate it.

Legalization in the District is fused with the weighty issues of civil rights and drug arrest rates among African Americans. In faraway Western states that have legalized marijuana, those issues have been largely secondary to civil liberties and drug safety.

View Graphic Support for legalized marijuana in D.C.

A band of pro-marijuana activists supporting Initiative 71, in fact, have almost no money in their campaign account and may not run a single ad, but support seems increasingly hardened in part because of a major shift toward support among African Americans.

The District’s black residents, who now account for half its population, once opposed marijuana legalization, partly out of fear it could lead to addiction among black youths. But as new studies have suggested otherwise, that attitude has evolved. One study last year showed that blacks account for nine out of 10 arrests for simple drug possession in the District, while another showed that was the case even as usage likely varied little among races.

According to the poll, 56 percent of likely African American voters say they would vote for legalization, a near identical number to a broader question about support for legalization asked in a Washington Post poll in January. Together, the polls confirm a complete reversal of opinions among African Americans from four years ago. Then, 37 percent were in favor of legalization and 55 percent opposed.

The District’s rapidly changing demographics also help explain the possible success of the initiative. In four years, the population in the District has swelled by 45,000, or 7.4 percent, and many newcomers are young, white and increasingly affluent. More than 7 in 10 voters in these groups support legalization.

All that puts the District far to the left of the legalization discussion nationally with the country closely divided at 49 percent in favor and 48 percent opposed, according to a Washington Post-ABC News poll earlier this year.

Nina Moiseiwitsch, 19, a college student studying biomedical engineering in New York, said she is certain to vote absentee in the District to be heard on the marijuana issue.

The government and police “have better things to focus on than trying to keep on top of something they really can’t,” she said. “I think it’s a distraction from . . . harder drugs that really are a problem in D.C. And it could become safer once regulated.”

Activists collected more than 57,000 signatures to qualify the measure for the ballot. They pushed forward even as some pro-marijuana groups urged restraint, concerned legalization in the District risks forcing Congress to react.

As it is, votes will be held in the District, Alaska and Oregon to decide legalization in November. Alaskans voted down a similar measure a decade ago but also have no criminal or monetary fines for possession.

The measure in Oregon led by a bare majority in a poll five months ago. Voters in Florida also appear certain to approve a medical marijuana measure in November.

The measure would allow people 21 and older to possess as much as two ounces of marijuana for personal use and to grow up to three marijuana plants at home.

To keep from triggering a prohibition on ballot measures that run afoul of federal law, Initiative 71 does not spell out that the District would allow for the sale of marijuana. That would be left up to regulations to be written and approved by the next mayor and D.C. Council. They also would have broad power to alter the measure.

Against that backdrop, the increasing likelihood that Initiative 71 will pass could force candidates for mayor — Democrat Muriel Bowser, a council member representing Ward 4; David A. Catania, an at-large council member running as an independent; and Carol Schwartz, a former council member also running as an independent — to offer more thorough explanations on their views of the issue.

Bowser and Catania have said they would vote for legalization, but neither has shown a propensity for direct conflict with federal law enforcement over drug laws. Schwartz opposes legalization.

During the council debate on decriminalizing marijuana in the spring, Bowser supported doing so, but she said allowing residents to possess marijuana begged the question of how they would come to obtain it. “Dealing with how people can procure this decriminalized marijuana has to be the second step,” she said.

Catania was instrumental in establishing the District’s medical marijuana program, but for years he sought to do so cautiously, in order to not draw the scrutiny of federal agents based in the District that enforce federal drug laws.

Catania, however, was among the most vocal supporters of decriminalization and sought to confront U.S. Rep. Andy Harris (R-Md.) this summer when he attached a provision to a federal spending bill that could undercut the District’s effort to reduce fines for possession to $25.

Still, a vote for legalization would require more of the next mayor, including following through with whatever plan might be approved to sell and tax the plant and to prepare for the almost certain attempts by Republicans such as Harris to interfere with the plan in Congress.

The NBC4/Washington Post/Marist poll was conducted Sept. 14 to 16 among a random sample of 1,249 D.C. adults reached on conventional and cellular phones. The margin of sampling error is plus or minus four percentage points among the sample of 572 likely voters.