Ted S. Warren / AP Marijuana is weighed and packaged for sale at the Northwest Patient Resource Center medical marijuana dispensary Oct. 10, 2012, in Seattle.

The barrage of television ads started in August. In a series of spots airing throughout the state of Washington, marijuana advocates called on voters to approve Initiative 502, which would legalize the recreational use of cannabis for people over 21. The ads’ protagonists, however, were not aging hippies or medical-marijuana proponents; they were law-enforcement leaders with frontline experience in the war on drugs. Two were former U.S. Attorneys, and one was the former head of the FBI in Seattle.

The ads underscore the unprecedented support I-502 has garnered among Washington’s law enforcement and political elite. Besides the two U.S. Attorneys, Seattle’s mayor, the entire city council and both candidates for sheriff of King County (encompassing Seattle) all support the measure, which would allow the state to tax marijuana’s production and sale. Virtually all of them cite the failure of the federal government’s 40-year drug-war policy — one centered on prohibition — and tout the measure as a way to curtail drug-related crime and cut into drug cartels’ mammoth profits.

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“We’ve tried criminalization. It’s an abject failure,” John McKay, who served as U.S. Attorney in Seattle from 2001 to 2007, tells TIME. McKay says Washington is awash in marijuana from gigantic hydroponic operations in lower British Columbia, which the Royal Canadian Mounted Police say are worth roughly $25 billion a year. Most of that cannabis crosses the U.S. border through what used to be McKay’s district. “Millions and millions of Americans smoke marijuana, and since it’s illegal, they inadvertently fund criminal activity. The way you get the market back is, you make it legal for businesses to compete for it.”

There are growing signs that Washington voters may heed McKay’s advice. A poll conducted in September by SurveyUSA showed that 57% of respondents will vote for I-502, while 9% remain undecided. On Election Day, that support should be enough to see I-502 approved, say drug-policy experts, who are also monitoring marijuana-legalization propositions in Oregon and Colorado. The Washington poll coincides with a national survey conducted by Gallup in October showing that 50% of Americans believe marijuana use should be legal.

In Washington, arguments for approving I-502 have centered on the high economic cost of enforcing marijuana laws — and on the measure’s massive potential for state coffers. I-502 would place a 25% tax on all marijuana transactions, and the resulting revenue would add up to $1.9 billion within five years, according to the Washington State Office of Financial Management. Fifty percent of that revenue would go to the state’s basic health plan, while substance-abuse-prevention programs would receive 15% of revenue.

“Prohibition has absolutely failed,” Seattle City Attorney Peter Holmes tells TIME. Upon election in 2010, Holmes stopped prosecuting misdemeanor marijuana cases, focusing limited law-enforcement resources on violent crime instead. “We need to reorient law-enforcement priorities and say, Let’s stop criminalizing adult private conduct as long as it doesn’t create a public safety problem.”

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I-502’s DUI provision is credited with amassing the most support, especially among the part of the populace that was both conservative and skeptical. The measure’s driving-while-stoned provision would set a maximum intoxication limit of five nanograms of THC (marijuana’s active ingredient) in the blood, which is comparable to a 0.08 blood alcohol content, the legal limit in Washington. Experts say the lack of a DUI provision has kept similar marijuana initiatives from winning approval in other states, mostly notably California.

But the DUI detail doesn’t sit well with all people. Although there is no organized opposition to I-502, the DUI provision has riled voters who typically favor legalizing marijuana. Medical-marijuana advocates have come out against I-502, arguing that the DUI detail would create a new legal risk for users because THC remains in the blood stream for days, even months, after consumption. They say medical-marijuana users would test positive for THC whether they are impaired or not.

Nevertheless, if I-502 is approved, the measure’s most formidable opposition will come from the federal government, which states explicitly that marijuana remains illegal under federal law. Holmes and McKay nonetheless remain cautiously optimistic regarding possible federal action, encouraged by the federal government’s tactics in Washington so far. In September, they point out, federal law-enforcement officials sent letters to 23 medical-marijuana dispensaries, warning they would be shut down if found to be within 1,000 ft. (300 m) of a school or playground. That advance warning, as opposed to unannounced raids, is a clear sign of restraint, says Holmes. “If the federal government can be convinced that we can cut cross-border shipments of large quantities of drugs, then I think they might see how we can cooperate, how we can allow this to go forward.”

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