The City of Portland fired a shot across Multnomah County's bow on Wednesday, opening what promises to be a prickly skirmish over whether the county will put a library taxing district on the November ballot.

The city's Office of Management and Finance, overseen by Mayor Sam Adams, says that ballot measure will hurt the city, and yesterday it said why.

The OMF brief says that creating the Multnomah County Library District would cost the city $7 million a year in property taxes—including a $1 million cut to the Portland Children's Levy.

The city also accuses Multnomah County of playing a shell game to pass a tax hike, using the library as a cover for increasing its general fund.

"Effectively," the brief says, "the majority of increased taxes from a new library district would go to supplant funding from Multnomah County's General Fund, not increase the library's budget."

Multnomah County still hasn't decided whether to pursue its library taxing district this fall, or wait until 2014. But Multnomah County Chair Jeff Cogen shot back at Portland officials this morning.

"Hearing the city's tone," Cogen tells WW, "brings to mind my grandmother's favorite expression: That is chutzpah."

Cogen continued: "To have the city self-righteously whining about, 'How dare the county impact our general fund!' to me brings to mind the bully on the beach, who spent the summer kicking sand on the little skinny kid, getting outraged when at the end of the summer the skinny kid gets up and decides to get himself a sandwich."

His outrage emerges from Portland's history of urban renewal districts, which have long shrunk county general-fund budgets.

It also shows the political pressures Multnomah County faces as it decides whether to pursue a permanent library taxing district. 

One fact unmentioned in the city's brief: A library taxing district would sit on the same November ballot as a Mayor Sam Adams-backed Creative Advocacy Network arts tax, an income tax measure to restore arts and music classes to Portland elementary schools.

The county commission will decide on July 31 whether to place the taxing district on the November ballot. County insiders say it's not a done deal. A three-year levy to continue funding libraries passed by a huge margin—84 percent of the vote—in May, but county libraries still slashed hours on July 1, closing all branches on Mondays.

The county is holding listening sessions at its library branches to gauge support; the last one is tonight in Hollywood.

The reason it's such a delicate decision is a bugbear in Oregon property tax law called "compression." Thanks to Measures 5 and 50, property tax rates are capped. So every new taxing district added to the region cuts into the slices of property tax revenue other levies can collect. In other words, each new slice of tax pie makes the other slices thinner.