The new president had a skeptical streak when it came to the value of regulation, influenced by his friend Cass R. Sunstein, a Harvard Law professor who had long argued that the government should more rigorously assess the benefits of new regulations. Mr. Obama liked that idea so much that he named Mr. Sunstein to lead the White House office that oversees rule-making.

“The president is not somebody who is intuitively or inherently a regulator,” said Howard Shelanski, who followed Mr. Sunstein in that role in mid-2013. He said Mr. Obama conveyed a simple message: “‘If we can get a good result without regulating, let’s do that.’”

But after eight years of a Republican administration, many Democrats were eager for the government to lean more forcefully on the levers of regulatory power, and officials within the federal bureaucracy felt emboldened.

The White House did resist some ideas. It shut down efforts by Lisa Jackson, Mr. Obama’s first administrator of the Environmental Protection Agency, to increase the regulation of ozone, a decision that environmentalists viewed as a betrayal.

But other rules were allowed to proceed. Kate Hanni, an advocate from Napa, Calif., for the rights of airline passengers, had tried for years to persuade the government to address a series of incidents in which flight delays left passengers trapped for hours on planes that had already left the gate, often in cabins with stinking toilets, weak air-conditioning and no food. The Bush administration put Ms. Hanni on a task force consisting mostly of airline executives, which concluded in the fall of 2008 — over her forceful and repeated objections — that the public was best served by allowing the airlines to make their own decisions.

Weeks after the task force released its report, Ms. Hanni was invited to Washington in December 2008 to meet with Robert S. Rivkin, the head of Mr. Obama’s transportation transition team. Democrats in Congress had introduced legislation to address the issue, but Mr. Rivkin asked Ms. Hanni if she would support new regulations instead. She would back anything enforceable, Ms. Hanni said.

“Right answer,” he replied.

Over the course of the next nine months, Mr. Rivkin and his team of career regulators at the Department of Transportation developed rules prohibiting planes loaded with passengers from sitting on the tarmac for more than three hours.