On the day last week when tensions erupted over the Legislature's snub of Gov. Mark Dayton's top priority — universal preschool — Education Minnesota launched a $200,000, monthlong TV ad blitz to build support for the measure.

The stakes for the union couldn't be higher. Fully phased in, public preschool is expected to cost $914 million in 2018-19 and require 2,849 licensed teachers, according to the Minnesota Management and Budget Office and the state Department of Education. Dayton has called for initial funding of $343 million in his budget ­recommendations.

The fight for public preschool is the latest example of the political muscle the state teachers union wields at the Capitol, where it has long been a powerhouse with an enviable win-loss ratio. This year, the union has been at the center of the action, from pushing back attempts to neuter teacher seniority protections, to arguing for more generous school funding and smaller class sizes.

One of the state's largest unions, Education Minnesota represents some 70,000 teachers, support staff and some college educators across the state, who frequently make their case to legislators in person. The union has deployed nearly two dozen lobbyists for the session, including the former executive director of Alliance for a Better Minnesota, the massive DFL funding network that helped fuel Dayton's re-election.

"Education Minnesota is the most powerful special interest" in education policy, said Sen. Branden Petersen, R-Andover, and "one of the most powerful interests ­overall at the Capitol."

Since its inception in 1998, when the state's two largest teachers union merged, Education Minnesota has gained a reputation for aggressive ­tactics and the ability to ensure DFL legislators vote in their interests.

Rep. Carlos Mariani, DFL-St. Paul, learned the hard way what happens when the teachers union is crossed.

A strong supporter of labor unions and collective bargaining rights, Mariani sponsored a measure in 2010 that would have given midcareer professionals an alternative path to a teaching license. That put the lifelong Democrat at odds with the union.

"They really went after me, including a couple of years later, organizing a local effort to unseat me," said Mariani, who was then chairman of the House education policy committee. Mariani said he "learned a lot" about the mind-set of big institutions and "darker stuff" about ­politics and the exercise of power.

Former Republican Gov. Tim Pawlenty, who clashed repeatedly with the union over his proposal to tie teacher pay to performance and other reform efforts, says that Education Minnesota's size, ­tactics and superior organizing make it one of the most influential and feared interest groups at the Capitol.

"They're really powerful, with a lot of money," he said in a recent interview, "and when they kick, they kick back hard, so you gotta be willing to put your mouth guard on."

Education Minnesota President Denise Specht downplayed Pawlenty's characterizations of the union as overly aggressive.

"I think that perhaps our influence right now is overstated, just like in the past our demise was maybe exaggerated," she said, noting that "we haven't always gotten our way."

Under Dayton, Education Minnesota successfully ­lobbied for all-day kindergarten, won increases in general state aid, special ed and higher ed funding. It also got legislators to eliminate a controversial requirement that certain measures of student achievement be used in teacher ­evaluations.

Less successful have been efforts to gain more funds for a recently implemented teacher evaluation law. With the Legislature's rejection of the universal preschool proposal last week, that priority for both Dayton and Education Minnesota is also now in jeopardy.

The preschool fight has become particularly rough. Dayton last week ripped into legislators for not including it in their education bills. Both the GOP-controlled House and the DFL-led Senate have given it a chilly reception. Save for Education Minnesota, no other interest group has stepped forward to ­support the proposal and many longtime early education advocates have come out in ­opposition.

"Why offer preschool ­primarily through public schools when we have nationally renowned private schools?" said Art Rolnick, a former senior vice president at the Federal Reserve Bank of Minneapolis and leading expert on the benefits of early-childhood education.

One of the first advocates of early education, Rolnick said he is "confused and disappointed" at the union's stance against early learning scholarships. "The union is one of our most powerful political organizations and advocates for education in Minnesota," he said. "Given that we have one of the largest achievement gaps in the country and given that early learning scholarships are proving to be so effective in achieving school readiness, the teachers union should be the strongest supporters for these scholarships, not some nerdy economist."

Dayton, who taught for several years in New York City schools in the late 1960s and early '70s, says education is a core value for him, and he believes firmly that all children should have access to high-quality preschool. He also is a longtime backer of labor, and defends the right of teachers, through their unions, to have a strong voice at the Capitol.

"They're very influential, and I think they deserve to be," he said of Education Minnesota, noting that business groups also wield tremendous influence in Minnesota politics.

Dayton, whom the union calls the "Education Governor," addressed teachers Saturday at their annual business meeting in downtown Minneapolis, voicing support for teachers and public schools.

Educators gathered to ­discuss state and federal education issues, including calling for a reduction in standardized testing that teachers say reduces students to nothing more than test scores. Many rank-and-file teachers have also called for more support of students living in poverty or in need of mental health counseling.

The governor closed out the annual convention by urging delegates to lobby legislators in support of his universal preschool plan, which he said would help close the state's glaring achievement gap.

"Now is the time to make the push," Dayton told delegates. "Now is the time, these next four weeks … Believe me, they need to hear from every one of you and every one of your members, every one of your friends and families, especially legislators in your districts. Hold them to the test."

He also criticized proponents of preschool scholarships, accusing them of ­ideological attacks against public schools and unions.

"They don't like public schools," Dayton said, adding "They don't like unions, and they especially don't like Education Minnesota — and I mean they really don't."

Dayton hasn't always seen eye-to-eye with the teachers union. In 2010, Education ­Minnesota endorsed his primary opponent, former House Speaker Margaret Anderson Kelliher for governor.

"We don't agree on everything," Dayton said in a recent interview. "We didn't agree on the teacher evaluation [law] in 2011 when I worked with the Republican leaders of the Legislature, and worked that out, although I was certainly sensitive to their concerns."

Mobilizing members

Education Minnesota is not the biggest spender at the Capitol. The Minnesota Chamber of Commerce and the Minnesota Business Partnership typically spend more.

But money isn't everything, and the union's best asset may be the sheer number and persistence of its members.

"Telling our story is ­crucial," said Jeanette Olson, a Cloquet social studies teacher who was at the ­Capitol recently with a dozen other northern Minnesota teachers who had come down for the day. Lawmakers, she said, "need to know what it's like in the trenches. They need to know what we face on a daily basis." More than 300 teachers have paid such visits since January and more will do so in the coming weeks.

Senate Majority Leader Tom Bakk, DFL-Cook, said teachers are among his most vocal constituents.

"I would say that they do as good a job as anybody — probably the best at — when an issue is in front of the Legislature, contacting their elected officials," said Bakk, himself a former union negotiator. "You never want to dismiss the importance of that."

Last in, first out

This year, Education Minnesota is fighting a two-front war. In addition to pushing the preschool program, they are fending off serious attempts to chip away at seniority protections for teachers.

The GOP House has passed a bill to make performance a factor in deciding which teachers are retained or laid off, something now determined almost exclusively by seniority. But the measure has run aground among ­Senate DFLers.

Democrats have fended off changes to the seniority system even though Minnesota is now one of only 10 states where teacher job security is determined largely by hiring date. Senate leaders say that layoff procedures are best left to negotiations between school boards and bargaining units.

Bakk, who is among those cool to the governor's preschool plan, puts seniority in a different category. Taking seniority protections away, he said, is part of broader attempts to curb labor unions' power and collective bargaining rights.

"There's this kind of a divide-and-conquer mentality with the labor movement, that if you just can get a crack in the armor … that eventually you can break the back of labor," he said.

Ricardo Lopez • 651-925-5044