“I will use the president’s long-recognized Impoundment Power to squeeze the bloated federal bureaucracy for massive savings,” Trump said in a plan posted last year. “This will be in the form of tax reductions for you. This will help quickly to stop inflation and slash the deficit.”

That pledge could provoke a dramatic constitutional showdown, with vast consequences for how the government operates. If he returns to office, these efforts are likely to turn typically arcane debates over “impoundment” authority — or the president’s right to stop certain spending programs — into a major political flash point, as he seeks to accomplish via edict what he cannot pass through Congress.