According to the measure's language, that money would be placed in a special fund and spent on research dealing with cancer, heart disease, emphysema, "and other tobacco-related diseases", as well as prevention programs.
Tobacco giant Philip Morris is expected to spend big to defeat the measure. It's arguing that the measure lacks acccountability to taxpayers, since the funding would be overseen by a new panel of political appointees.
The anti-Prop 29 campaign is trying to capitalize on the public's distrust of Sacramento.
"Now is not the time for Lance Armstrong to come into our state and ask us to support a flawed measure...to create another big-government spending program," said California Taxpayers Association President Teresa Casazza in a statement released Wednesday.
Prop 29 is just the latest effort to tax tobacco products in California.
The state already has an existing cigarette tax and tobacco products surcharge that, collectively, adds up to 87 cents per pack.
The relative lack of ballot measures in June means that voters will be seeing a lot of Prop 29 TV ads this spring as this fight heats up.
It's not just Armstrong's money, of course, but his fame that will help tobacco opponents in what is typically a lopsided spending battle.
Because this tax targets only a specific group of consumers, it will be far different from the tax battles that loom on the November ballot.