Over the past few weeks Monsanto, DuPont and other large corporations have flooded California with millions of dollars in ads against Proposition 37, which would require the labeling of food containing genetically modified ingredients. Two new polls confirm the well-funded negative campaign has managed to significantly reduce support for the ballot measure.

The California Business Roundtable/Pepperdine University School of Public Policy poll shows support for Prop 37 has dropped dramatically since last month. Their current poll finds 48.3 percent plan to vote for Prop 37, 40.2 percent plan to vote against it, and 11.5 percent remain undecided. Last month the same pollster found Prop 37 leading 66.9 percent yes to 22.3 percent no.

A SurveyUSA poll from this week confirms the large drop. It shows Prop 37 still leading but only by a very small margin. According to their poll 39 percent say they are certain to vote for it, 30 percent say they plan to vote no, and 31 percent are currently not certain about how they will vote.

The GMO labeling initiative still technically leads at this point so it might win approval from the voters, but its chances of passing are now seriously in doubt. It went from looking like a sure bet before the big corporate funded blitz to a potential loss now.

This is a powerful reminder how important unlimited corporate spending can be in politics. While the inherent partisan divide among voters makes it tough for advertising to significantly move many voters in top ticket races, it can have a major impact on how voters perceive issues and ballot initiatives.

The big chemical and food companies know Prop 37 could have ramifications beyond California so they are sparing no expense to kill it.