Mr. Daschle, a national co-chairman of the Obama campaign, said in a telephone interview on Friday that his role advising the Obama campaign on energy matters was limited. He said he was not a lobbyist for ethanol companies, but did speak publicly about renewable energy options and worked “with a number of associations and groups to orchestrate and coordinate their activities,” including the Governors’ Ethanol Coalition.

Of Mr. Obama, Mr. Daschle said, “He has a terrific policy staff and relies primarily on those key people to advise him on key issues, whether energy or climate change or other things.”

Ethanol is one area in which Mr. Obama strongly disagrees with his Republican opponent, Senator John McCain of Arizona. While both presidential candidates emphasize the need for the United States to achieve “energy security” while also slowing down the carbon emissions that are believed to contribute to global warming, they offer sharply different visions of the role that ethanol, which can be made from a variety of organic materials, should play in those efforts.

Mr. McCain advocates eliminating the multibillion-dollar annual government subsidies that domestic ethanol has long enjoyed. As a free trade advocate, he also opposes the 54-cent-a-gallon tariff that the United States slaps on imports of ethanol made from sugar cane, which packs more of an energy punch than corn-based ethanol and is cheaper to produce.

“We made a series of mistakes by not adopting a sustainable energy policy, one of which is the subsidies for corn ethanol, which I warned in Iowa were going to destroy the market” and contribute to inflation, Mr. McCain said this month in an interview with a Brazilian newspaper, O Estado de São Paulo. “Besides, it is wrong,” he added, to tax Brazilian-made sugar cane ethanol, “which is much more efficient than corn ethanol.”

Mr. Obama, in contrast, favors the subsidies, some of which end up in the hands of the same oil companies he says should be subjected to a windfall profits tax. In the name of helping the United States build “energy independence,” he also supports the tariff, which some economists say may well be illegal under the World Trade Organization’s rules but which his advisers say is not.

Many economists, consumer advocates, environmental experts and tax groups have been critical of corn ethanol programs as a boondoggle that benefits agribusiness conglomerates more than small farmers. Those complaints have intensified recently as corn prices have risen sharply in tandem with oil prices and corn normally used for food stock has been diverted to ethanol production.