As of Wednesday morning, the vote on the proposed $1-per-pack cigarette tax in California was too close to call, the Associated Press reports.

The measure, which was popular among voters earlier this year, lost support due to a $50 million campaign funded by the tobacco industry. The campaign raised questions about who would oversee revenue raised by the measure, how it would be spent, and whether it would stay in the state.

It could be days, or even longer, before the outcome is determined, according to the AP.

A poll released last week found 50 percent of likely voters said they supported the measure, while 42 percent were opposed, and 8 percent were undecided. In March, the measure had greater support. A survey found 67 percent of likely voters said they would vote for the measure, known as Proposition 29.

The initiative attracted national attention. Supporters include New York Mayor Michael Bloomberg and seven-time Tour de France winner and cancer survivor Lance Armstrong.

The proposal calls for 60 percent of the money raised to be used to support research on the prevention, diagnosis, treatment and potential cures for tobacco-related diseases. An additional 15 percent would be used to build or lease facilities, or to be spent on equipment, while 20 percent would be used for tobacco prevention and cessation programs. The remaining 5 percent would be used for law enforcement programs to reduce illegal sales to minors and smuggling, and administrative costs.[polldaddy poll=6292095]