Federal prosecutors disclosed this week they are developing a potential national security case against Yujing Zhang, the 33-year-old Chinese woman charged with unlawfully entering Mar-a-Lago with a stash of electronic equipment.

They asked a federal judge to allow them to file “classified information” under seal without the public — or the defendant — seeing it. If the motion is granted, prosecutors will present the evidence directly to the federal judge in Zhang’s trespassing case during a private, closed meeting in the judge’s chambers.

The prosecution’s motion indicates that she is a focus of a widening U.S. probe of possible Chinese espionage and suggests that authorities have evidence she was likely not simply a “bumbling tourist” who accidentally found her way into President Donald Trump’s private estate in Palm Beach.

The motion by a counterintelligence prosecutor with the U.S. Attorney’s Office suggests that authorities have relevant classified evidence that could pose a risk to national security should anyone — including Zhang — ever see it...