MADISON, Wis. (AP) — The race for Wisconsin's top education official pits a two-term incumbent backed by public school advocates and Democrats against two more conservative opponents who want to expand the private voucher program and undo the Common Core curriculum.

Incumbent Tony Evers faces John Humphries, a former administrator turned consultant in Dodgeville, and Lowell Holtz, a former teacher, principal and superintendent who is now retired. Racine math teacher Rick Melcher is running as a write-in.

The top two in Tuesday's primary advance to the April 4 general election. Turnout is expected to be low; the past three such primaries have averaged around 6 percent. It's the only statewide contest this year.

The winner will oversee the Department of Public Instruction, which runs K-12 education policy, curriculum and programs and administers state and federal aid for all 424 public school districts. The department also works with private schools in the choice program and runs teacher licensing and regulation.

Evers has held the job since 2009 after spending eight years as deputy. While the position is officially nonpartisan, Evers draws support from Democrats and groups that typically align with them, including teachers unions.

Evers says he offers a more optimistic vision for education in Wisconsin, while his opponents want to "create this dark cloud that everybody's failing."

Humphries and Holtz have attacked Evers from the right. Evers doesn't support expanding the statewide private school voucher program, arguing that it diverts needed resources from public schools. Humphries and Holtz argue that school choice programs should be expanded, saying they offer alternatives to parents unhappy with public schools and competition forces improvement.

Humphries and Holtz say Evers has been ineffective at closing a gap in achievement between white and other students, and hasn't improved graduation rates, test scores and college attendance for non-white students. Evers argues he's helped make progress in Milwaukee and wants to direct more money to students in poverty and rewrite the complex school aid formula.

"We have seen some small gaps closing," Evers said. "Is it enough? No. We will continue to work on it."

Evers calls it a success that Gov. Scott Walker is calling for about as much more funding for schools over the next two years as Evers has.

Humphries and Holtz accused each other of being liars at Capitol news conference Friday.

Humphries called the event to discuss a job offer that Holtz allegedly presented to him at a breakfast meeting in December. Humphries alleged that Holtz offered him a $150,000 state job, along with a driver, and broad authority to run or reorganize the state's five largest school districts if he dropped out of the race.

Holtz responded by saying that it was Humphries, not he, who was lying about the alleged deal. Holtz said the ideas were a "rough draft" and came from a business leader that both he and Humphries have refused to name. Humphries said Holtz came up with the proposal and was lying about his involvement in crafting it.

Holtz, who pitches himself as the most conservative candidate, has adopted the slogan "kidservative." He ran for state superintendent in 2009 but came in last in a five-person primary.

This time Holtz has the backing of some of the most vocal conservative voices in the state, including the anti-abortion, anti-gay marriage group Wisconsin Family Action, the Republican Party in four counties, the Pro-Life Wisconsin Victory Fund and 22 Republican state lawmakers.

Holtz emphasizes that he's the only one of the three who didn't sign the Walker recall petition. He also supported the Act 10 law that took away teachers' collective bargaining rights while working as a school superintendent.

Holtz said he supports a "voucher in every backpack," but he's also said he wants to make every public school stronger.

"Kids could care less whether you're a Republican, a Democrat, or a liberal," Holtz said. "They don't care. What they care about is, are you interested in them?"

Humphries has tried to cast himself as the in-between candidate.

"There's a big space in the middle," Humphries said. "People who are concerned with improving outcomes are the folks who will be most focused on my candidacy. I'm the one who can knock Evers out of this race."

Humphries' campaign is co-chaired by Democratic state Rep. Jason Fields, who favors school choice, and Republican Rep. Jeremy Thiesfeldt. Humphries, like Evers, signed the petition to recall Walker.

Humphries has tried to win over conservatives with a series of proposals. They include creating a state school board to oversee powers of the superintendent, redoing the state report card in a way that would label more schools as failing, and establishing a process to allow low-performing public schools to be converted into private charter or voucher schools.

Evers has outraised his opponents by more than 4-to-1 this year and had 15 times as much cash on hand as either Humphries or Holtz as of Feb. 6. But Evers and his backers say they are prepared for pro-voucher outside groups to spend heavily after the primary.

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