Trump asks Supreme Court to shield his tax returns from prosecutors, setting up historic separation-of-powers showdown

President Trump asked the Supreme Court on Thursday to stop a prosecutor’s investigation of his personal finances, a bold assertion of presidential power that seeks a landmark decision from the nation’s highest court.

The filing by the president’s private lawyers represents a historic moment that will test the court and highlights the Constitution’s separation-of-powers design. It also marks a new phase in the investigations that have dogged Trump throughout his presidency and have culminated in an impeachment inquiry.

The case involves Manhattan District Attorney Cyrus Vance Jr.’s attempt to enforce...