Mr. McCain has voiced support for this research, but he now adds that he hopes it will soon be unnecessary to use these cells. In his response to the Science Debate 2008 questionnaire, at sciencedebate2008.com, Mr. McCain said the nation should refuse “to sacrifice moral values and ethical principles for scientific progress.”

Mr. McCain’s campaign did not respond to repeated requests for information. According to the journal Science, he has “no formal structure” for seeking science advice. It reports that Douglas Holtz-Eakin, a former economic adviser and head of the Congressional Budget Office under Mr. Bush, serves as Mr. McCain’s “point man” on science, having been in touch with experts on climate, space and “science in general.”

On the other hand, Mr. Obama established a science advisory committee led by Dr. Harold Varmus, a Nobel laureate who is president of the Memorial-Sloan Kettering Cancer Center. Dr. Varmus said the group’s leaders communicated almost daily with the campaign’s policy leaders. And this month, the campaign announced that 61 American Nobel laureates in science had endorsed Mr. Obama. (When Martin Chalfie, a Columbia biologist, learned last week that he had won the Nobel Prize in chemistry, he said one of the first things he did was to call one of the 61 to ask how to add his name to the list.)

Dr. Varmus acknowledged that finding the money to pay for the Obama innovation agenda “is not an easy question.” But he said Mr. Obama would focus on federal spending on high priority areas “and among the things he mentioned as being central to economic recovery are science and technology.”

Experts agree that the immediacy of the financial crisis is overshadowing the innovation debate and predict little headway until a new president has settled into office and confronts budgetary realities.

“The problem,” said Mr. Boehlert, the former chairman of the House science committee, who left Congress last year, “is that it takes an immediate investment that won’t pay immediate dividends, and people are looking for an instant fix.”