Crafting smart public policy often requires asking the right question. That thought occurred when Carrie Lucking, Education Minnesota's policy director, took the microphone as part of a May 8 Twin West Chamber of Commerce panel on the 2015 Legislature's debate over early education.

A consensus has emerged at the State Capitol about early education's importance, Lucking said. "The only real question that a lot of us are posing is: What are we going to do with the 4-year-olds?" She made a strong case for the answer preferred by Gov. Mark Dayton: bring tuition-free preschool for 4-year-olds to every school district in the state.

An expression resembling a scowl crossed the visage of the panelist seated beside her, Art Rolnick. He's the former Minneapolis Fed senior vice president who has become a national policy guru on early education. I asked him afterward to verbalize his pout.

"That isn't the right question — not for this year," Rolnick said. There's a question more pressing: How best can Minnesota close the achievement gap?

He'd poked Minnesota's sorest point. The persistent lag in poor, nonwhite kids' academic performance compared with that of their more affluent white peers is arguably the biggest threat to this state's future prosperity, given the rapid population growth on the lagging side. Research shows that quality early ed can narrow that gap, producing a long-term rate of return greater than nearly any other tax dollar spent, the economist said.

Rolnick has spent the better part of the last dozen years fashioning a public-policy answer to the achievement-­gap question. His preferred strategy targets aid at kids who are most at risk of underachiement. It begins with prenatal assistance to low-income parents, follows up with home visits after a child is born and provides scholarships that allow parents to choose from among a variety of quality-rated programs. Children as young as age 1 can benefit.

No matter how the Legislature's regular session ends Monday night, we first-drafters of history can already say that the 2015 session produced a breakthrough for early education. For the first time, preschool became a top gubernatorial priority and a key moving part in end-of-­session dealmaking.

But it's also been the year when a split in early-ed ranks was laid bare. Advocates divided into two surprisingly disputatious camps — those who want to expand state-funded scholarships to every eligible poor child vs. those who prefer to launch preschool programs for 4-year-olds in every school district in the state.

This session's argument may be settled shortly. But because it's related to a bigger division of Minnesota opinion, the early-ed split is not likely to go away — not without considerable effort on the part of both camps to come to agreement on the right question. It's an effort I hope they make. They'll do this state a favor if they do.

The bigger difference is about public education. Once a haven of bipartisanship at the Legislature, public education has acquired a partisan tinge it lacked 30 years ago. The teachers union has become more tightly allied with the DFL, and the GOP has become the home base of religious conservatives who prefer home and parochial schooling.

Meanwhile, the achievement gap's persistence has called into question the competence of the educational institutions that tax dollars support.

The latter-day push for an early-ed remedy to the achievement gap arose about a dozen years ago outside public education circles. Many of the pushers were allied with the business community and had a partisan coloration of their own.

Against that backdrop, Rolnick's scholarship design that the Minnesota Early Learning Foundation (a business-funded group) piloted a few years ago looked suspiciously like a Republican private-school voucher program in public school eyes. And DFLer Dayton's call for universal pre-K looked like a teachers union power grab to scholarship fans. The question under discussion too often has been which adults, or which party, would win or lose under competing proposals — not what would do the most to help struggling kids learn.

Seemingly lost was this: Nothing would improve public education's reputation in this state more than narrowing the achievement gap. Teachers, in particular, ought to be all for policies proven to yield better results among children most at risk. Scholarships can claim that proof.

Lucking explained why universal preschool is a worthy response to her question about 4-year-olds. Public schools are already in the right places and equipped with child-friendly facilities. They are staffed with licensed, accountable teachers. They can align their preschool curriculum to dovetail with the lessons of kindergarten and the elementary grades that follow.

All that has merit — plus this: Minnesota parents spend more on child care than their counterparts in all but two other states. Tuition-free public preschool would be a boon to family finances. It's an idea whose time seems coming.

But if the question is how to close an achievement gap that's leaving a fast-growing share of the population undereducated, the scholarship approach should take precedence. It offers parental engagement, scheduling flexibility, cultural diversity and earlier-than-age-4 intervention that a one-size-fits-all public school cannot. As the governor's own Early Learning Council recommended on April 30, "Children at greatest risk of school failure should be prioritized."

How can Minnesota best help those children? After this session and for some years to come, that will be the right question.

Lori Sturdevant, an editorial writer and columnist, is at