Jason Furman, a newly appointed senior economic adviser to Obama, said his preliminary response is that the report's findings bear out what Obama's campaign has been saying: that he's for the middle class.
"Middle-class families get tax cuts that are three times larger from Obama than from McCain," Furman said. "And the McCain plan gives nearly one-quarter of its benefits to households making more than $2.8 million annually - the top 0.1%."
Douglas Holtz-Eakin, senior economic adviser to McCain, noted that the report does not take into account the spending reforms - such as eliminating earmarks - that are central to McCain's strategy to support tax relief and help reduce the deficit.
One of the center's co-directors, William Gale, conceded in a conference call that "if McCain succeeds (in achieving his proposed spending cuts), the fiscal cost of his plan does go down."
But spending cuts can be politically difficult to achieve, said Len Burman, the Tax Policy Center's director.
Holtz-Eakin characterized McCain's plan as one geared toward "reshaping federal bureaucracies and protecting taxpayers' money. [His] plan is based on kicking down doors in Washington, and delivering tax dollars back to the American taxpayers who are struggling with record gas prices, soaring food costs and a down economy."
Not the final word
Williams said the Tax Policy Center analysis should be viewed as a work in progress. Researchers plan to update it as they get more information about the plans from the campaigns and if the candidates introduce new tax policies between now and Election Day.
The center will also incorporate the tax elements of McCain's and Obama's health care proposals when they update their findings.
How the candidates' tax plans would affect economic growth is an open question. "It depends on how the deficits are closed," Burman said.
Tax studies have shown that when tax cuts are deficit funded and they're paid for by raising taxes in the future, "the economy is worse off than if you didn't cut at all," Burman said.
