Oregon Gov. Kate Brown has announced her support of the controversial corporate tax Measure 97, the proposed corporate tax increase that will raise $3 billion a year in new tax revenue.

"I support Measure 97 because there is a basic unfairness in our tax system that makes working families pay an increasing share for state and local services, including public schools, senior services, and health care," Brown says in a statement released by her reelection campaign.

The measure is expected to dominate Oregon's fall election cycle, with national corporations and labor unions already throwing heavily-funded attacks at each other.

Measure 97, backed by union-funded group Our Oregon, has already attracted some high-profile opponents, including Intel and Emily Powell, owner of Powell's books.

The measure would significantly increase taxes on big corporations in Oregon. Any corporation with more than $25 million in sales would have to pay a minimum of $30,000 a year, plus a 2.5 percent tax on all sales above $25 million. The current tax rate is 0.1 percent on sales and is capped at $100,000.

The war between Our Oregon and local companies is already heated: Last month, WW reported how insurer The Standard and tech giant Intel both threatened to pull funding for Portland nonprofits if they backed the tax.

Brown's endorsement ends months of speculation about her position on the measure. She has repeatedly refused to take a position. In June, she talked about how she would spend the $3 million but didn't endorse the tax. That same month, former Gov. John Kitzhaber blasted Brown for waffling.

Brown said she was just being careful.

"I think that it's more important that I get the decision right than have it be done quickly," she told OPB in June.

The measure's backers are rejoicing.

"With her endorsement, Gov. Brown is joining a movement that includes more than 600 endorsers working to hold large, out-of-state corporations accountable to pay their fair share," writes Otto Schell of the Oregon PTA. "Measure 97 will markedly improve the lives of Oregon families and students."

Brown's endorsement drew criticisms as well. Mike Phillips, spokesman for the "no" campaign on Measure 97, says the tax is still going to lose.

"Measure 97 would give politicians and bureaucrats a $6 billion dollar raise and a blank check to spend it any way they want," Phillips says in a statement. "While some politicians may like that idea, we doubt the majority of Oregon taxpayers and voters will."

Bud Pierce, Brown's Republican opponent in the governor's race, said he was not surprised by the endorsement.

"It took her more than 300 days to take a stance," Pierce said in a campaign statement. "Months ago she released how she would spend the money raised by this increase, which showed that she obviously supported the measure, but was afraid to take an unpopular position."

House Republican Leader Mike McLane (R-Powell Butte) is also dismissive.

"Governor Brown's support of Measure 97 was the worst kept secret in Salem," he said in a statement. "Today, she apparently decided it was time to come clean with Oregon voters. Now let's see how many other Democratic candidates are going to be honest with voters about their support for the largest tax increase in Oregon history."

Here's Brown's full statement.

Governor Brown Announces Positions on Qualified Ballot Measures

Portland, OR — Governor Kate Brown today announced her positions on five ballot measures that have qualified for the ballot in the 2016 general election.

“As Governor, it is important for Oregonians to know where I stand on issues they will be asked to decide in November,” Governor Brown said.

Governor Brown’s positions on the ballot measures are as follows:

Business Tax Increase Initiative – YES

Outdoor School Lottery Fund Initiative – YES

State Funding for Dropout Prevention and College Readiness Initiative – YES

Wildlife Tracking Prevention Act – YES

Oregon Lottery Proceeds for Veterans’ Services Amendment – YES

Judicial Retirement Measure – YES

Business Tax Increase Initiative, Measure 97 (formerly IP-28): Yes

“I have spent my career fighting to make Oregon a place where everyone can thrive. I support Measure 97 because there is a basic unfairness in our tax system that makes working families pay an increasing share for state and local services, including public schools, senior services, and health care. By some measures, Oregon is among the lowest in corporate taxes, and Oregonians expect everyone to pay their fair share.

“Our state cannot move forward and meet Oregon’s growing needs over the next decade without a more stable revenue base. Measure 97 is an important step forward, and I will make sure the funds the measure yields go towards schools, health care, and seniors, as the voters expect.

“State leaders before me have repeatedly tried and failed to solve the problem of adequate and stable funding for schools and other state services. Every solution has had strengths and weaknesses in terms of fairness and economic impact. None has succeeded in bringing the business community, individual and family taxpayers, service providers, and advocates together.”

Outdoor School Lottery Fund Initiative: Yes

“There’s no better way to develop a bond with our natural environment than spending time outdoors. That connection is an important part of growing up in Oregon and is fundamental to instilling the values of conservation in our children.

“While I support the measure, I will preserve funding for important economic development programs currently funded by the lottery.”

State funding for Dropout Prevention and College Readiness Initiative: Yes

“We have a responsibility to ensure Oregon’s children have access to quality education and the support they need to learn and prepare for success in a global economy. There’s no question that the narrowly targeted initiatives under this measure can positively impact graduation rates and other top priorities for local schools, and help develop a skilled workforce Oregon businesses need.

“This measure complements my work to create a seamless system of education that expands early learning opportunities, and supports students at each stage of their learning to develop the knowledge and skills they need to find a job they want and thrive here in Oregon.”

Wildlife Trafficking Prevention Act: Yes

“I’m proud of Oregon’s widely known reputation of protecting threatened species. State law should reflect these values.”

Oregon Lottery Proceeds for Veterans’ Services Amendment: Yes

“Oregon’s veterans and their families deserve our deepest thanks and dedicated resources to ensure their health, education and economic opportunity.”

Judicial Retirement Measure, Amendment 1: Yes

“It’s important that we eliminate age discrimination in Oregon is essential to the integrity of Oregon’s legal process.”