Mr. Deese’s role is unusual for someone who is neither a formally trained economist nor a business school graduate, and who never spent much time flipping through the endless studies about the future of the American and Japanese auto industries.

Image Brian Deese, who interrupted his law school career, is the little-seen force behind the revamping of the American auto industry. Credit... Stephen Crowley/The New York Times

He lives a dual life these days. He starts the day at a desk wedged just outside of Mr. Summers’s office, where he can hear what young members of the economic team have come to know as “the Summers bellow.” From there, he can make it quickly to the press office to help devise explanations for why taxpayers are spending more than $50 billion on what polls show is a very unpopular bailout of the auto industry.

Several times a day he speed-walks to Treasury, taking a shortcut through the tunnel under the colonnade, near the kitchens. The other day he talked about how sharply perceptions of the industry’s future changed after Mr. Obama’s election.

“At the first meeting with Rick Wagoner,” he said, referring to G.M.’s recently deposed chief executive, “they were in a very different place. He said publicly that bankruptcy was not a viable option. It’s been a long process getting everyone to look at the options differently.”

In fact, from before Inauguration Day, few in Mr. Obama’s circle saw any other choice. Every time Mr. Deese ran the numbers on G.M. and Chrysler, he came back with the now-obvious conclusion that neither was a viable business, and that their plans to revive themselves did not address the erosion of their revenues. But it took the support of Mr. Rattner and Ron Bloom, senior advisers to the task force charged with restructuring the automobile industry, to help turn Mr. Deese’s positions into policy.

“The president’s instruction to us was that we had to come up with a solution that would work on a commercial basis, that didn’t involve indefinite federal financing,” Mr. Deese said. “But we didn’t want liquidation, which would have even worse effects. So the question was how do you design a very substantial restructuring, and do it fast.”