Measure 97, the corporate tax measure, is now the costliest ballot initiative fight in Oregon’s history. The campaigns for and against it have raised more than $33 million.

Measure 97 would increase taxes on companies with more than $25 million in annual sales in Oregon.

Its opponents have now raised just shy of $23 million in cash contributions. That breaks a record set in 2014 by the fight over labeling GMOs in food.

Opponents of the GMO labeling bill raised $21.2 million, while proponents raised $8.4 million. It was defeated by fewer than 1,000 votes.

Fred Meyer, Safeway and Costco have each contributed $1.8 million to the No On 97 campaign. Lithia Motors, Cambia Health Solutions and Comcast are also top donors.

The Yes On 97 campaign, meanwhile, has raised more than $10.5 million. The top backers are all unions, including groups that represent most of the state’s workforce: teachers, state employees and healthcare workers.

There is no limit on how much individual donors can contribute to state ballot measure campaigns, and television stations raise the price of ads during elections, so the cost of ballot measure campaigns is steadily rising.