The voter initiative to allow the use of medicinal marijuana in Arizona moved closer to passing Friday when the "yes" tally on Proposition 203 took a significant lead after having trailed since Election Night.

As early ballots continue to be counted, the "yes" votes for the Arizona Medical Marijuana Act outnumbered the "no" votes for the first time, leading by 4,421 late Friday.

For more than a week, the "no" votes had led by at least 3,000 each day. There were 8,000 early ballots and 2,000 provisional ballots, mostly in Maricopa County, left uncounted Friday night. Officials will work through the weekend to try to finish tabulating them.

Prop. 203 supporters, including a marketing group that set up a model medical-marijuana "dispensary" the week before elections, began celebrating Friday night.

Early results had shown those who voted at the polls on Nov. 2 or submitted their ballots before Election Day rejected the measure by a slim margin. But the margin began to shrink once election workers started counting provisional ballots and early ballots dropped off at polls. By Friday's count, the "yes" side had gained about 7,000 votes to surpass the "no" side.

Andrew Myers, campaign manager for the pro-Prop. 203 Arizona Medical Marijuana Policy Project, attributed the lead to provisional ballots and said he was optimistic they would help the measure pass. "As it stands right now, I'm confident that when the count is complete, we'll be ahead," Myers said.

Voters cast provisional ballots when there is a question about the voter's eligibility. For example, voters who show up at the wrong place or do not have proper identification cast provisional ballots.

Provisional voters tend to be younger people whose addresses do not match the voter roll because they move around often, Myers said.

A Rocky Mountain Poll released last month indicated 67 percent of voters under 35 years old supported the measure. Poll results are based on interviews with 555 registered voters conducted by phone Oct. 1 to 10.

Myers said the "yes" campaign did not target younger voters. The deadline for counties to finish tabulation was the end of the day on Friday. But Maricopa County can continue counting ballots into next week, according to Matt Benson, director of communications for the Secretary of State's Office.

The measure needs a margin of less than or equal to 200 ballots to trigger a recount.

Carolyn Short, chairwoman of the anti-Prop. 203 campaign Keep AZ Drug Free, said she was disappointed by Friday's updated figures. The under-35 voter group "is not an age group that has been particularly supportive of our position."

Short said she believes the pro campaign did target the younger audience and remained hopeful the "no" vote would win. Keep AZ Drug Free tried to reach as many people across the state as possible, but it had limited funds, she said.

"I think that there are some voters, I believe, who voted for a concept," Short said. "And the concept is the so-called medical marijuana for seriously ill people. They will find that anybody who wants marijuana will get it and anybody with a marijuana card will get special treatment."

If it passes, Prop. 203 will go into effect after the general-election canvass on Nov. 29.

The debate over Prop.203 has centered on whether medical marijuana would end up being used only by patients with serious diseases. Supporters used the phrase "stop arresting patients" to tout the potential medical benefits of marijuana. But opponents have said that Prop. 203 is a back door to legalization.

The U.S. Food and Drug Administration has not approved smoking marijuana for medicinal use.

If voters approve the measure, licensed physicians could recommend medical marijuana to patients with debilitating medical conditions, including cancer, glaucoma, HIV/AIDS, hepatitis C and Alzheimer's disease.

Patients would register for identification cards with the state health department. They could receive up to 21/2 ounces of marijuana every two weeks from dispensaries or cultivate up to 12 plants if they live 25 miles or farther from a dispensary.

There would be 124 dispensaries operated by non-profits to start, proportionate to the number of pharmacies in the state.