The U.S. Chamber of Commerce has twice now been mentioned in the 2008 presidential debates — and it’s not Republican contender Sen. John McCain (Ariz.) who’s using the country’s pre-eminent business lobby machine to back up his debating points.

It’s Democratic nominee Sen. Barack Obama (Ill.).

On Wednesday night, the two had moved onto health care, and Obama was criticizing a piece of the McCain plan that would replace the exclusion for employee-paid health care premiums — which currently are not part of one’s taxable income — with a tax credit.

Critics say such a change would encourage younger, healthier workers to opt out of their employer health care plans, take the tax credit, and buy their own insurance on the open market, possibly at cheaper rates.

That, in turn, would shrink an employers’ health-care pool, making it harder for the employer to negotiate with insurers, ultimately hurting the quality of those plans.

“And don’t take my word for it,” said Obama, about halfway through the hour-and-a-half debate. “The U.S. Chamber of Commerce, which generally doesn’t support a lot of Democrats, said that this plan could lead to the unraveling of the employer-based health care system.”

Just nine days earlier, Obama had also relied on the chamber to criticize McCain’s plan to eliminate the tax exclusion.

“In fact, just today,” he said, referring to an Oct. 7 New York Times article, “business organizations like the United States Chamber of Commerce, which generally are pretty supportive of Republicans, said that this would lead to the unraveling of the employer-based health care system.”

In fact, the “business organizations” were responding to a question from Times reporter Kevin Sack, who asked representatives of several business groups what they found objectionable about the McCain plan.

The chamber’s James Gelfand, its senior manager on health policy, told Roll Call that Obama correctly characterized the chamber’s view on exclusion. But, he said, Obama left out an important caveat.

“We have strong criticisms of both plans,” Gelfand said. “Both need a lot of work.”

Obama’s plan to create an employer mandate for health care coverage or pay additional taxes is one idea with which the chamber strongly disagrees. Said Gelfand: “It’s not time to be creating a new health care tax.”

Although the chamber leans strongly Republican, it does not always back the GOP party platform.

“There have always been Republicans who had different ideas on health care than business, people who think the best thing to do is to separate health insurance from the employer-sponsored system. Business,” he said, “doesn’t agree with that for a number of reasons.”