The first group includes officials like Peter R. Orszag, the budget director, and Dr. Ezekiel J. Emanuel, the medical ethicist whose brother Rahm is the chief of staff. The second includes Rahm Emanuel and Nancy-Ann DeParle, the director of the Office of Health Reform, who must contend with the realities of getting legislation passed.

“Let’s be honest,” Rahm Emanuel said in a recent interview. “The goal isn’t to see whether I can pass this through the executive board of the Brookings Institution. I’m passing it through the United States Congress with people who represent constituents.”

He went on: “I’m sure there are a lot of people sitting in the shade at the Aspen Institute  my brother being one of them  who will tell you what the ideal plan is. Great, fascinating. You have the art of the possible measured against the ideal.”

Mr. Orszag would not be interviewed. But in an e-mail message sent through a spokesman, he said the current legislation “lays the foundation” for cost-cutting over the long-term, adding: “Will more need to be done in the future? Absolutely.”

Senator Susan Collins, the Maine Republican whose vote the administration is courting, convened a news conference on Monday with Senator Lamar Alexander of Tennessee, a member of the Republican leadership, to spotlight her concerns over cost containment. Ms. Collins said she had been meeting with a group of moderate Democrats who shared her views.

“I don’t believe we need more pilot projects to show us that health care delivery reforms are necessary,” she said in an interview. She added, “I think people are much more upset over the cost of care than the administration is acknowledging.”

Both the House and the Senate are proposing cost-saving measures. The House bill projects $440 billion in Medicare savings over 10 years; the Senate Finance Committee bill projects about $420 billion. White House officials say there will be additional, substantial savings in the private sector, as well. But how much is not clear.