The initiative to legalize the personal possession and home cultivation of marijuana will be embraced by campaigners as residents of the US capital is all set to vote next week.
If adopted on Tuesday, Initiative 71 would mark another milestone on the road towards wider acceptance of pot in the United States, where under federal law it is still considered as potent as heroin or LSD.
"I'm very confident it's going to pass," said Adam Eidinger, chairman of the DC Cannabis Campaign, which is spearheading the initiative.
"I don't know by how big a margin. I'm hoping for over 60 percent... I don't think there's a single precinct that our initiative will fail in."
Colorado was the first US state to legalize marijuana, followed by Washington state, in both cases after voter initiatives.
Similar votes are taking place Tuesday in Alaska and Oregon, as well as in two towns in Maine.
Florida voters are being asked to cast their ballots on whether their state should join 23 others that already permit doctors to prescribe medical marijuana to seriously ill patients.
Support for legalization appears to run strong in the capital district, where 57,000 people signed a petition over three months earlier this year in favor of putting Initiative 71 on the ballot -- more than double the number required.
The proposal is sharing the ballot with Washington's city council election, and enjoys the support of mayoral race frontrunner Muriel Bowser.
- Legal sales by 2016? -
Public opinion polls point to success for the yes camp, with a Washington Post survey in September finding support among likely voters running at two-to-one.
Eidinger, a veteran local activist, self-described hipster and co-founder of a local head shop called Capital Hemp, said Initiative 71 is by design "an incomplete law."
It would make it lawful for anyone over 21 in Washington to possess up to two ounces (57 grams) of marijuana for personal use, grow no more than six cannabis plants in his or her home, give -- but not sell -- up to one ounce to another person, and to sell or use cannabis paraphernalia.
Speaking with AFP at DC Cannabis Campaign's crowded headquarters, incongruously located in Washington's staid embassy district, Eidinger said a yes vote would open the way for city council to draft tax-and-regulate legislation enabling the public retail sale of pot.
"We could expect legal sales of marijuana in stores in Washington sometime in 2016," said Eidinger, 41.
"In the meantime, people won't be arrested, and they'll be able to grow (marijuana) for themselves. We'll go through a little bit of a transition."
Indeed, in a forward-looking public hearing Thursday, a municipal council committee considered a draft bill that would permit the sale of marijuana, with one official estimating the potential market at $130 million a year in a city of 650,000 where 15 percent are already thought to be consuming pot.
Among local voters, opposition appears strongest among older, more conservative African-Americans, even though young black Washingtonians have been the ones most likely to be arrested for pot possession, according to an American Civil Liberties Union study.
But their numbers are not expected to be sufficient to forestall Initiative 71.
Going forward, one potential stumbling block to legalization is Congress.
Since the District of Columbia home to Washington is not a state, with no voting representatives on Capitol Hill, local laws can in theory be upended by members of Congress who come from other parts of the country.
Doing so, however, runs the risk of being seen as denying the democratic will of Washingtonians, at a time when the capital -- after decades of urban decay and skyrocketing crime -- is undergoing a renaissance with a strong influx of affluent Millenials.
Eidinger said a yes vote on Initiative 71 could force Congress to tackle the status of marijuana at the federal level head-on, potentially leading to the repeal of its ranking as a hardcore drug that's subject to stiff criminal penalties.