Foes of Initiative 522 have spent $14.3 million so far attacking the food labeling initiative and it is paying off.

The latest Elway Poll found the measure has lost nearly one-third of its support in the past month. That is when the No on 522 committee began airing television commercials and mailing out literature on the purported warts of the measure requiring labels on foods containing genetically modified ingredients.

I-522 is leading 46 percent to 42 percent with 12 percent undecided in the survey of 413 registered voters conducted Oct. 15-17 by Seattle pollster Stuart Elway.

That’s a big tumble from mid-September when Elway found 66 percent of voters endorsed the initiative and only 21 percent opposed.

Not surprisingly, advertising is changing people’s minds.

Three out of four voters who had seen only ads for one side or the other planned to vote in the direction of the ads they have seen, he wrote in an analysis of the results.

“Those who have seen no advertising planned to vote ‘yes’ by a 17-point margin — about the same margin the ‘yes’ side had before the advertising blitz began,” Elway wrote.

For the Yes on 522 committee — which has spent $5.4 million — the silver lining is that the measure is still ahead.

And Elway says history favors them winning, too.

Since 1992, 17 of 22 initiatives which had support above 60 percent in Elway polls conducted in September wound up winning.

“Momentum is on the side of I-522 opponents, but history is on the side of proponents,” he wrote.