OF COURSE, we’re not really talking about a new tax for affordable housing. We’re talking about a tax for building affordable housing, buying and maintaining open space, and rehabilitating and preserving old buildings.

It’s important to remember that the CPA grew out of suburban communities’ need to control sprawl. In the 31 communities that have already passed CPA property-tax surcharges, the measure has been pitched as a way of purchasing open space and maintaining it. The state legislation specifies that money raised through the tax and the state match must be spent in the following way: 10 percent on affordable housing, 10 percent on open space, and 10 percent on preservation. The remaining 70 percent can be divvied up among these three claims as the town sees fit. Wherever the CPA has passed, activists have urged that the money be used to buy land — in large part to halt development, including construction of affordable housing. Here in Boston, in fact, the Committee for a Better Boston has identified 30 projects that should be immediate recipients of money raised through the tax surcharge. They’re great ideas, ranging from cleaning up and restoring Doherty Playground in Charlestown (which was designed by Frederick Law Olmsted) to renovating the South End’s Hotel Alexandra as affordable housing. But 14 of the 30 ideas are related solely to open space and preservation.

In fact, there’s little evidence that the CPA will do much to solve Boston’s housing crisis. A study commissioned by the Citizens Housing and Planning Association, an organization that strongly supports the CPA, concludes that communities that implement the CPA must put more emphasis on affordable housing for the statewide law to have any meaningful regional impact on the problem.

Beyond these questions, though, is a much bigger one: if Question One passes, who will make decisions about how the discretionary money raised by the CPA is spent? The Boston ballot question specifies that a nine-member commission will be formed. Members will be appointed by the mayor. The committee will make recommendations to the mayor and the Boston City Council, both of which will have the final say. In other words, the mayor, who is unequivocally ambivalent about Question One, will have the most influence over how the money is eventually spent. Do we really want the guy who squandered a decade’s worth of prosperity on stalled development projects like waterfront rehabilitation and the Red Sox stadium to make these decisions for us?

Six months ago, the city could afford to spend $200 million on a new park for the Red Sox. If Question One passes, it will raise $50 million over two years. We don’t need a tax surcharge. We need a new set of priorities.

Susan Ryan-Vollmar can be reached at svollmar[a]phx.com