Joey Bear.

A small nonpartisan research center operated by professed “geeks” has found itself at the center of a rancorous $5 trillion debate between President Obama and Mitt Romney.

No white paper or policy manifesto put out during the presidential campaign has proved more controversial than an August study by the Washington-based Tax Policy Center, a respected nonprofit that issues studiously detailed tax analyses.

That study found, in short, that Mr. Romney could not keep all of the promises he had made on individual tax reform: including cutting marginal tax rates by 20 percent, keeping protections for investment income, not widening the deficit and not increasing the tax burden on the poor or middle class. It concluded that Mr. Romney’s plan, on its face, would cut taxes for rich families and raise them for everyone else.

The detailed paper proved kindling for a political firestorm. Mr. Romney criticized the center as performing a “garbage-in, garbage-out” analysis and his campaign accused it of partisan bias. The Obama campaign used the center’s numbers to argue that Mr. Romney had proposed a $5 trillion tax cut. Economists jumped on the bandwagon too, flinging analyses back and forth and picking apart the projections and assumptions in the report.

At the Tax Policy Center itself, responses ranged from irritation at the partisan nature of some attacks to incredulity over the political hysteria. “There was this résumé-hunting, White-House-visitor-log” searching feel to the response, said the center’s director, Donald Marron, a former Bush administration economist. “That was unanticipated,” he added dryly.

In many ways the report did just what the center was created to do: inject some solid numbers into a shifty, accusatory, raucous political debate. The decade-old center — a joint project of the Brookings Institution and the Urban Institute, two nonpartisan grandes dames of the Washington world — was founded precisely to “fill that niche,” Mr. Marron said.

“A lot of tax policy discussions are — how to describe them? — people yelling at each other,” he said. “We believe that good information leads to better policy discussions and ultimately better policy outcomes.”