The fate of California's controversial Proposition 29, a proposed tax on cigarettes, was still unclear early Wednesday.
Just before 1 a.m. (4 a.m. ET), one percentage point separated the sides in the battle over the proposed law that would raise taxes on every pack of cigarettes by $1, yielding an estimated $735 million a year for the state.
With close to 70% of the precincts reporting, the preliminary vote tally stood at 49.5% in favor and 50.5% against the law, election officials said.
Opponents of the law say three-quarters of money raised would go to cancer research.
"The American Cancer Society, the American Heart Association and the American Lung Association wrote the initiative carefully," Lori Bremner of the American Cancer Society told CNN's "Sanjay Gupta MD."
"The money is going to be invested in cancer research here in California and on tobacco prevention and cessation programs to protect kids and reduce smoking here in California."
Studies show the tax will help decrease smoking and save lives, she said.
But those opposed slam the tax as a misguided burden in an already tough economy.
"What we're seeing in the state of California is a lot of frustration on the part of our citizenry that it's just another tax," said Dr. Marcy Zwelling, a general practitioner. The tax, she said in an interview with CNN, "goes to build bigger bureaucracy, build business, build buildings, not necessarily to go to cancer research."
The opposition in California was fueled by a huge influx of cash from big tobacco. About $47 million was raised in efforts -- including TV advertising -- to defeat "Prop. 29," including $27.5 million from Philip Morris and $11 million from R.J. Reynolds, according to figures from MapLight, a nonpartisan research firm.
About $12 million was raised in support of the bill, including $8.5 million from the American Cancer Society and $1.5 million from the Lance Armstrong Foundation, known as Livestrong. Armstrong himself appeared in ads urging people to "vote yes on 29." (Gupta, CNN chief medical correspondent, is a board member of the foundation.)
There is already an 87-cent tax on each pack of cigarettes in California.
According to California's official voter guide, the health groups behind Prop. 29 say it will "save lives, stop kids from smoking, and fund cancer research," while those opposed say the initiative "doesn't require revenue be spent in California to create jobs or fund schools."
Bremner insists the campaign against Prop. 29 has traded in "deceptions." The biggest misconception is that the money collected "will be somehow wasted or used otherwise," she said.
But Zwelling says it will heavily affect poorer Americans, who are more likely to smoke. And other efforts, including the state's ban on smoking in public places, have succeeded at pushing people to quit smoking, she says.
John Seffrin, CEO of the American Cancer Society, says if the bill passes, "It would make California the second-largest funder of cancer research after the (National Cancer Institute) in the entire country."
Some grant proposals that currently go unfunded would find a source of revenue, he said.
"So, it's a tremendous opportunity for California to do the right thing -- not only for California, but for the whole world."
CNN's Caleb Hellerman, Nadia Kounang and Josh Levs contributed to this report.