A raid on state support for DFL-dominated Minneapolis and St. Paul has become so routine when Republicans are in control at the State Capitol that the big cities' howls of protest barely register on news radar.

But I couldn't overlook the plight of Duluth. It's as Greater as Greater Minnesota gets, and a member of the statutory First Class Cities Club only by being grandfathered in a few decades ago. It hasn't surpassed that elite group's requisite 100,000 population since the 1970 census. In the 2010 decennial count, Duluth came in just north of 86,000 and ranked fifth among Minnesota cities, behind both Rochester and Bloomington.

Yet along with Minneapolis and St. Paul, Duluth would lose a huge chunk of local government aid (LGA) under the House budget — this in a year in which a new House Republican majority vowed to be Greater Minnesota's protectors.

Two-thirds of Duluth's annual LGA allotment — $19.9 million — would disappear. By comparison, the hits in Minneapolis and St. Paul would be $34.4 million and $30.3 million, respectively.

Those cities are larger and richer than Minnesota's port city. In Duluth, $20 million is a quarter of the city's annual operating budget. One could lay off the entire Duluth police force and not quite save $20 million. If you scrapped the entire fire department, you'd still have to find $5 million more in cuts.

You say you'd prefer to raise taxes than dismantle public safety? The city portion of every property tax bill in town would need to double to avoid cuts.

Why Duluth? Like Minneapolis and St. Paul, Duluth gets more LGA per capita than the state average, Republicans say — as if LGA were intended for distribution on a per-capita basis.

It's not. LGA helps older cities that swell by day with disproportionately more workers than residents. Such places have infrastructure and public-safety demands that exceed what can reasonably be financed by property taxes alone. State aid keeps property taxes affordable and the level of public service fairly even across the state.

Curiously, the House didn't take from Minneapolis, St. Paul and Duluth to give to other, smaller cities. Rather, the House tax bill applies the $85 million thus saved to assorted tax cuts, the largest being a rollback of business property taxes.

One other plausible explanation for the GOP cut is obvious: Like Minneapolis and St. Paul, Duluth voters generally elect DFLers.

A shot at Duluth as brutal as this one is indefensible in a conference committee in which DFL senators sit on the other side of the table, hammering out a bill that requires a DFL governor's signature to become law. When the final version of the tax bill appears, I expect the LGA cuts for all three cities to be gone.

But not forgotten — I hope. I hope the rally to Duluth's defense is big enough to produce a residue of regret that can stand as a cautionary bar in both parties' memories the next time either is tempted to pick on one portion or population of the state for what look like partisan reasons. Legislators ought to come away from this session with renewed intention to think of Minnesota as one state.

Duluth's lamentably lame-duck Mayor Don Ness spoke well last week: "I like to think we're better than that as a state — that we recognize the value and importance of all parts of this state. We all contribute to the success story that's happening all over this state."

Nearly three years after a whopper of a flood, Duluth is rebounding nicely, Ness said. "We're seeing an influx of private investment that we haven't seen in over a half-century. That both broadens our own tax base and allows us to be a financial stimulant for the state and a contributor to the state budget."

Ness fears that Duluth's resurgence would end abruptly if city services were slashed or property taxes hiked. "It would mean losing the forward momentum we've been showing," he said. The same goes for St. Paul and Minneapolis, he hastened to add. "It would be devastating for all of us."

To their credit, elected leaders in smaller cities agree. The Coalition of Greater Minnesota Cities has rallied around their threatened member — and Minneapolis and St. Paul — as fiercely as if the lot of them were facing an LGA cut. They seemed to be arguing out of self-interest as much as fraternal loyalty.

"The House GOP's attempt to impose dramatic cuts to first class cities threatens the long-term viability of the LGA program," coalition president Heidi Omerza of Ely said in a statement. She's right: If one party is allowed to use LGA as a partisan reward and/or punishment, both parties shortly will. A tit-for-tat thus started can expand well beyond LGA and continue for years at the Capitol, damaging the whole state's vitality over time.

The contagion may have already spread beyond LGA. Witness the House's stingy response to a loan request from Cirrus, an aircraft manufacturer that is seeking a $4 million loan through the Minnesota Investment Fund to build jets in Duluth. The Senate said yes; the House responded with $2 million.

At the House's level, the project is at risk, according to Senate Majority Leader Tom Bakk. If the House prevails in the economic development conference committee and the Cirrus project goes elsewhere as a result, a cycle of partisan retaliation over economic development will be set in motion that will ill-serve this state. And I'd guess that Bakk will see to it that voters who have never heard of Cirrus today will know a lot about it come Nov. 8, 2016.

Lori Sturdevant, an editorial writer and columnist, is at lsturdevant@startribune.com.