At a wide range of departments and agencies, Mr. Trump’s political appointees are going to extraordinary lengths to try to prevent Mr. Biden from rolling back the president’s legacy. They are filling vacancies on scientific panels, pushing to complete rules that weaken environmental standards, nominating judges and rushing their confirmations through the Senate, and trying to eliminate health care regulations that have been in place for years.

In the latest instance, Treasury Secretary Steven Mnuchin declined to extend key emergency lending programs that the Federal Reserve had been using to help keep credit flowing to businesses, state and local governments and other parts of the financial system. He also moved to claw back much of the money that supports them, hindering Mr. Biden’s ability to use the central bank’s vast powers to cushion the economic fallout from the virus.

Terry Sullivan, a professor of political science and the executive director of the White House Transition Project, a nonpartisan group which has studied presidential transitions for decades, said Mr. Trump was not behaving like past presidents who cared about how their final days in office shaped their legacy.

“They are upping tension in Iran, which could lead to a confrontation. The economy is tanking and they are not doing anything about unemployment benefits,” he said.