Acting attorney general Todd Blanche's decision to grant President Trump protection from I.R.S. audits is set to be a central issue in his confirmation hearing on Wednesday. The move marks an unprecedented intervention by the Justice Department into tax enforcement matters involving a sitting president.

Legal experts say the order raises significant questions about the separation of powers and the independence of the tax collection agency. The I.R.S. has traditionally operated with autonomy in audit selections, and presidential tax returns have been subject to mandatory examination since the Watergate era.

Democrats on the Senate Judiciary Committee are expected to press Blanche on the legal basis for the directive and whether it constitutes improper political interference. The hearing will also examine whether the acting attorney general consulted with career officials at the I.R.S. or the Justice Department's Office of Legal Counsel before issuing the order.

The controversy comes as Blanche seeks permanent confirmation as attorney general, with his handling of this matter likely to influence senators' votes on his nomination.