Mr. Mnuchin has promised that Treasury will release its analysis in full. Yet, just one day before the full Senate prepares to vote on a sweeping tax rewrite, the administration has yet to produce the type of economic analysis that it is citing as a reason to pass the tax cut.

Those inside Treasury’s Office of Tax Policy, which Mr. Mnuchin has credited with running the models, say they have been largely shut out of the process and are not working on the type of detailed analysis that he has mentioned. An economist at the Office of Tax Analysis, who spoke on the condition of anonymity so as not to jeopardize his job, said Treasury had not released a “dynamic” analysis showing that the tax plan would be paid for with economic growth because one did not exist.