It’s been a tough couple weeks for California’s Proposition 37, which would require that all genetically modified foods carry special labels.

The most recent polling on the measure, released three days ago, shows 39.1 percent in favor of the proposition, with 50.5 opposed. Undecideds were 10.5 percent, with a 3 percent margin of error. That’s just a few days after we last reported 44 percent in favor and 42 percent opposed.

In that time, opposition has raised an additional $3.3 million for advertising. Big food and chemical companies are pumping big cash into the no-on-37 campaign faster than you can say National Frozen Pizza Institute (shockingly, they’re in the no camp). In the last days leading up to the election, the spending has only intensified. Just yesterday, Coca-Cola contributed $235,000 and Biotechnology Industry Organization sent $250,000. No on 37 ads are clogging everything from Facebook to Hulu, even for green junkies like me.

There’s a bit of movement on the other side, including support from the Whole Foods camp. From Napa Valley Patch:

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Whole Foods officials formally announced the company’s support for Prop. 37 in September. But as the election approaches, additional signage is going up at its stores and employees throughout the state have been trained on GMOs and the ballot measure, [co-CEO Walter] Robb said … Whole Foods has put the bulk of its Yes on 37 efforts into social media and also has some radio ads that will become more prevalent in the days before the election.

Today the Proposition 37 campaign released new commercials aimed at debunking the assertion of big corporations in the anti-prop camp: that the measure would increase food costs.

Marisa Tomei, James Franco, Minnie Driver, James Van Der Beek, Stacy Keibler, Lisa Bonet, Molly Ringwald, and some other grown-up teen actors and people whose names I honestly don’t recognize star in new television and web ads.

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But the campaign’s biggest announcement today was an odd one. From SF Gate:

Four days before the election, it announced that the FBI has opened a criminal investigation into its opposition for feloniously using the seal of the United States Food and Drug Administration in its mailers — basically trying to make it look like the FDA endorses the No on 37 campaign — and held a telephone press conference.

The thing is? The feds say they aren’t investigating and never were.

Joe Sandler, a lawyer for the Prop. 37 campaign, said two weeks ago his staff contacted the office to complain about the misuse of the FDA’s official seal in the opposition’s campaign literature and was notified by a Sacramento FBI agent Thursday that investigators were looking into the allegation.

The Prop. 37 campaign hasn’t responded to the fallout from its allegations. Discussing the rumor of a federal investigation, a spokesman for the opposition said, “Desperate times call for desperate measures.” I can’t disagree — these are clearly desperate times. But this measure appears to have backfired.

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