Sen. Barack Obama spent much of this past weekend touting his health plan — and blasting that of Sen. John McCain. A poll out last week from the public opinion research team at the Harvard School of Public Health and Harris Interactive may suggest why.

Despite the ups and downs of this campaign, health care has been a perennial strong suit for Democrats; it's an issue on which voters have almost always favored them over the GOP. And indeed, the Harvard poll, conducted Sept. 17-21, found an overall preference for Obama's plan over McCain's. By 45-14 percent respondents without health insurance thought Obama's plan would be more likely to help them get coverage, and by 31 to 19 percent those currently covered thought Obama's plan more likely to help them keep insurance. And by 27-19 percent respondents said Obama's plan would be better at keeping down the amount they pay for health care and insurance.

But when asked which candidate's health plan would be better for them personally, the results were much closer — 33 percent said Obama's compared to 27 percent for McCain's. And among the coveted subset of political independents, McCain actually came out slightly ahead — by 26 to 24 percent. The poll has a margin of error of plus or minus 3.2 percentage points.

So Obama came out swinging.

 

Warns one new ad: "the McCain tax could cost your family thousands," a reference to the fact that along with the new tax credits McCain wants to provide for health insurance, he would also, for the first time, levy income taxes on the value of the insurance provided by employers. That coverage is currently tax-free.

McCain economic advisor Douglas Holtz-Eakin cried foul in a Sunday conference call with reporters. "you'd have to be getting an enormous amount of health insurance, one the middle class can only dream of, in order to have a tax liability," Holtz-Eakin said. For example, he says, a family getting an average health policy worth $12,000, even if they're in the top tax bracket, would still only pay $4,200 in taxes — still less than the $5,000 family credit.

But while that may be true for now, there's a catch, according to the Tax Policy Center, which analyzed the tax plans of both candidates. The McCain health plan indexes its tax credits not to the cost of health care, but to the cost of general inflation. Thus, as the years pass, the credit will be worth less and less compared to the price of health insurance premiums. That will not only make it more difficult for people to use the credit to buy their own insurance, it could subject more middle-class people to paying taxes on health insurance provided on the job — if they still get it, that is. The TPC estimates that by the year 2018, 20 million people will no longer have job-based health insurance coverage if McCain's plan becomes law.