SALEM — Opponents of a controversial corporate sales tax measure on the November ballot have reported raising $16.8 million to quash the proposal.

Two political action committees supporting Measure 97 have raised more than $7 million and spent nearly $3 million, according to the Secretary of State’s Office. The committees seeking to defeat the measure reported spending $11.6 million. Both sides filed a required campaign finance report by a late Tuesday deadline.

The Measure 97 appears to be on track to set a record for the most raised for a ballot measure contest, said Jim Moore, political science professor and director of the Tom McCall Center for Policy Innovation at Pacific University.

Opponents and supporters are “still sitting on piles of money to use to defeat or pass this thing,” Moore said.

The current record was set by Measure 92 in 2014, a proposal to require labeling of genetically modified foods. Opponents of that measure raised more than $20 million, while supporters raised $8 million.

Measure 97 would levy a 2.5 percent “gross receipts “tax on certain corporations’ Oregon sales exceeding $25 million.

The tax would bring in an estimated $3 billion per year in new revenue, representing the largest sales tax in the state’s history and boosting the state’s general fund by 25 percent.

Union-backed Our Oregon placed the measure on the ballot through the state’s initiative petition process. Supporters say the new money would help provide more sustainable and adequate funding for education, health care and senior services. Meanwhile, opponents point to estimates by the Legislative Revenue Office that show that the tax would increase prices and slow job growth in the state. A legislative lawyer also issued an opinion stating that legislators are not restricted to using the money for purposes Our Oregon intended.

Both big corporations and local business groups have opposed the measure. Some of the opponents’ recent contributions came from out-of-state mega corporations such as Comcast and Kroger/Fred Meyer, but the Craft Brew Alliance and Portland-based Jive Software also are among the contributors.

The campaign for the measure received contributions from the American Federation of Teachers and their Oregon chapter, the Oregon Education Association and Oregon AFSCME Council 75.

Fundraising could slow if there is any consistent polling showing the measure will be defeated, Moore said. So far, polls largely have shown the measure will pass, but the most recent poll by Portland-based Hoffman Research Group showed the measure would fail 47-to-41.