"This isn’t bias. These are numbers," Looney said. "It’s pretty plain math. It really is just algebra."

Looney acknowledged that the study didn’t examine Romney’s proposed spending cuts, in great part because Romney hasn’t specifically proposed them. Nor did the study analyze the effects of corporate-tax cuts because it assumed that the big business tax cuts Romney proposed would not add revenue to the budget.

Romney’s campaign, however, pointed to a study from another group, the conservative-leaning Tax Foundation, which estimated that a 10 percent corporate tax cut would increase average wages by 9 percent.

But the campaign couldn’t provide any analyses or studies of its own showing what effect a potential wage increase would have on Romney’s plan.

Looney countered that major corporate tax cuts in the past didn’t show the “substantial growth effects” being touted by Romney’s campaign.

The core of the Tax Policy Center’s analysis sought to examine the “trade offs” between Romney’s proposal to cut income taxes and the revenue he could gain from broadening the base of the tax code by eliminating tax breaks and preferences.

In that light, the study said, Romney’s plan to cut tax rates by 20 percent “would provide large tax cuts to high-income households, and increase the tax burdens on middle- and/or lower-income taxpayers.”

Romney’s tax reform plan keeps Bush-era tax cuts for all Americans, while Obama proposes eliminating those tax cuts on households earning more than $250,000 a year. Romney also wants to slash corporate taxes, eliminate the estate tax and keep investment taxes from increasing.

Romney has indicated the plan would pay for the $360 billion in annual tax cuts by eliminating tax breaks and by spending cuts. His campaign pointed out he would shave 5 percent from the non-defense federal budget his first year.

That could save about $145 billion. Where would the other $215 billion come from? The campaign won’t say yet.

In the absence of those specifics, the Tax Policy Center report — and the Florida-specific paper from the Obama campaign — said all scenarios lead to a net tax increase for the vast majority of taxpayers.

Here’s why: The rich pay more taxes and the major tax preferences disproportionately help the middle class relative to their incomes.

Conservatives defended Romney’s plan by pointing out that most studies criticizing it do not take into account potential budget cuts, which would offset the need for eliminating some tax breaks. They also pointed out that Obama’s tax plan would slam small businesses with higher costs, costing jobs.

Chris Edwards, director of tax policy for the conservative Cato Institute, said Romney’s plan wouldn’t necessarily shift the tax burden from the rich onto the middle class. Edwards said Romney could avoid that by coupling the tax cuts with adequate spending cuts.

“I’m in favor of the general approach of Romney’s tax cuts — eliminating loopholes, lowering the rates,” he said. “My angle on it would be it is Romney’s responsibility to match that revenue loss with spending cuts.”

Democrats counter with this argument: Romney’s spending cuts would hurt the middle class and the poor as well because he would reduce big-ticket popular programs such as Medicare, Social Security and Medicaid. If Romney proposes cutting those, Obama’s campaign will hammer him for hurting seniors and the poor.