The big corporate money that has bankrolled a round-the-clock TV ad blitz the past few weeks by those opposed to the statewide ballot measure to require labeling of genetically engineered foods is beginning to dramatically alter the dynamics of the campaign.

A new voter survey by Seattle pollster Stuart Elway still shows Initiative I-522 winning, but by a very narrow margin — 46 to 42 percent, with 12 percent of voters undecided.

In September, well before the print and TV advertisements began, the Yes on 522 campaign was breezing to victory, with an Elway poll showing the initiative passing by a whopping 66 percent to 21 percent margin

“If you were calling it today, you’d say it’s still going to pass,” Elway tells The Seattle Times today. “But the momentum shift — how’s that going to play out? And, it’s still within the [4 percent] margin of error.”

The poll, a sampling of 413 registered Washington voters, was conducted from Oct. 15 to 17.

As of Monday, the No campaign had raised $17.2 million in contributions -– a state record in terms of a warchest accumulated for an opposition effort to turn back an initiative — compared to nearly $6.1 million by the Yes campaign.