PHOENIX (AP) — Education is one of the top issues in Arizona's gubernatorial race after anger about stagnating school funding bubbled over into a six-day teachers' walkout this spring.

Three Democrats and one Republican primary challenger are running to unseat GOP incumbent Gov. Doug Ducey. He's cast himself as a champion of public schools, pointing to a three-year plan to give teachers a 20 percent raise in this year's budget. And he pledges that he's not done yet. But he's coming out strong against any proposal to raise taxes, saying it would harm business climate.

"If we raise taxes, we're going to kill our economy," he said. "These companies have options. They're going to go to Nevada or Utah or Texas."

Instead of raising taxes, Ducey's answer to better fund schools is to rely on increasing revenues from a growing economy.

All of Ducey's challengers have varying plans on how to fund schools, including tax increases or eliminating sales tax loopholes. They also have various opinions on the ballot initiative called the Invest in Education Act. The proposal would raise taxes on high earners to fund public education. It would apply to individuals who earn more than $250,000 a year and households that earn more than $500,000 a year.

Democratic candidate state Sen. Steve Farley:

Farley proposes eliminating $3 billion worth of sales tax loopholes and cutting the overall sales tax by 1 percent.

"If we find $3 billion worth, we could lower our sales tax rate by a full percent while increasing education spending by $2 billion a year," he said.

Farley says such a sum would be sufficient to restore cuts to education made after the recession plus add funding for other areas like pre-K and continued education.

"All of those things can be funded if we decide to prioritize our state budget on investing in ourselves instead of giving away to out-of-state corporations," he said.

Farley said there needs to be other policies beside the Invest in Education Act. He said the estimated $690 million the tax hikes would raise won't create enough new funding.

Democratic candidate Kelly Fryer:

Fryer, the former CEO of the YWCA of Southwest Arizona and a community activist, wants to revamp the tax code.

"My vision for Arizona is that the best school for every kid in every neighborhood in every county in our state is the local district public school," she said.

Fryer supports the Invest in Education Act. Prior to its rollout, she had a similar proposal to create two new tax brackets for high earners. She also advocates ending some sales tax exemptions, and adding a state tax on homes worth more than $ 1 million.

Fryer also wants to see the state end policies that give tax credits or scholarships for private schools and "put charter schools out of business."

"The reason we have so many parents sending their kids to charter schools is because the local public schools have been defunded and they're in trouble," she said.

Democratic candidate David Garcia:

Garcia, a second-time statewide candidate after running in the 2014 superintendent of school race, is adamant in his support of the Invest in Education Act. His campaign bus parked alongside the Red for Ed march route on the first day of the teacher strike in late April.

"We told people during Red for Ed, 'Wherever the teachers are going to go, we'll follow,'" he said.

In addition to income tax increases from the proposal, Garcia supports cutting back corporate tax credits to raise more revenue. He said Arizona should stop advertising itself as a cheap place to be.

"This state has been selling itself as cheap for a long time," he said. "I think we're underselling our state. It's a beautiful place to be."

Republican candidate Ken Bennett:

Bennett, a former state senate president and secretary of state, is running against Ducey in the primary. He said Ducey "caved" by proposing the teacher raises before the walkout, saying the plan to fund the pay hikes raises based on rosy economic projection isn't reliable.

Bennett doesn't support the Invest in Education Act and said he doesn't think raising new revenue is absolutely necessary — though he would like to see tax reform to create more state revenues that could be used for schools.

"I think we need to look at restructuring our tax system so it's broader based and has lower rates," he said.

He also wants to see a revamped funding formula, one that takes into account which schools have a below-average amount of funding and also rewards performance.