The ballot measure would suspend the implementation of the state's landmark greenhouse gas reduction law until the state's unemployment rate drops to 5.5 percent for four consecutive quarters.
Whitman says the measure is too simple a solution or too complex of a problem. Democratic candidate Jerry Brown praised Whitman's decision to oppose the measure.
More on that story: Whitman breaks silence on Prop 23
Now, there's a grassroots effort to get out the vote to defeat Prop 23.
Thursday night, Prop 23 was on many minds. The "No On Prop 23" campaign held 80 get out the vote parties all over the state, including one in Palo Alto.
"This is about stopping big oil," said Susan Frank from the "No On Prop 23" campaign.
Major oil companies are backing Prop 23, which aims to suspend the state's greenhouse gas emissions law -- AB32.
AB32 was supposed to take effect in 2012. Its goal was to bring down California's greenhouse gas emissions to 1990s levels, by 2020.
"AB32 is a job killer, it destroys jobs and needs to be suspended. That's exactly where our campaign is coming from," said Anita Mangels from the "Yes On 23" campaign.
The "Yes On 23" campaign insists now is not the time to put limitations on companies by adding regulations. The executive director of California's National Federation Of Independent Businesses says the unemployment rate will rise above the current 12 percent with AB32 because small business owners simply can't afford the guidelines right now.
"That's new cost in electricity, new costs in natural gas, new costs in actual gasoline. All of those effect main street mom and pops that are trying to keep our state going," said John Kabateck, a small business representative.
"AB32 is about regulating emissions from large power sources and large sources of pollution, like oil companies. It's not about affecting small businesses," said Frank.
Whitman said she plans to vote no on Prop 23, but would suspend AB32 for one year if voted governor.
"She doesn't want to look like she doesn't support growth of jobs in California. So I think she's really trying to walk a fine line here," said Santa Clara Associate Professor Nancy C. Unger, Ph.D.
Regardless, it's a move that is confusing to some voters because they see Whitman's actions of voting no on Prop 23 as pointless if she's going to suspend AB32 if voted governor.
Voters will have their say November 2.