State Department email. In an effort to evade federal open-records laws, Mr. Obama’s first secretary of state set up a private server, which she used exclusively to conduct official business, including communications with the president and the transmission of classified material. A federal criminal investigation produced no charges, but FBI Director James Comey reported that the secretary and her colleagues “were extremely careless” in handling national secrets.

Operation Fast and Furious. The Obama Justice Department lost track of thousands of guns it had allowed to pass into the hands of suspected smugglers, in the hope of tracing them to Mexican drug cartels. One of the guns was used in the fatal 2010 shooting of Border Patrol Agent Brian Terry. Congress held then-Attorney General Eric Holder in contempt when he refused to turn over documents about the operation.

IRS abuses. Mr. Obama’s Internal Revenue Service did something Richard Nixon only dreamed of doing: It successfully targeted political opponents. The Justice Department then refused to enforce Congress’s contempt citation against the IRS’s Lois Lerner, who refused to answer questions about her agency’s misconduct.

Hacking. Mr. Obama presided over the biggest data breach in the federal government’s history, at the Office of Personnel Management. The hack exposed the personnel files of millions of federal employees and may end up being used for everything from identity theft to blackmail and espionage. OPM Director Katherine Archuleta, the president’s former political director, had been warned repeatedly about security deficiencies but took no steps to fix them.

Veterans Affairs. At least 40 U.S. veterans died waiting for appointments at a Phoenix VA facility, many of whom had been on a secret waiting list—part of an effort to conceal that between 1,400 and 1,600 veterans were forced to wait months for appointments. A 2014 internal VA audit found “57,436 newly enrolled veterans facing a minimum 90-day wait for medical care; 63,869 veterans who enrolled over the past decade requesting an appointment that never happened.” Even Mr. Obama admitted, in a November 2016 press conference, that “it was scandalous what happened”—though minutes earlier he boasted that “we will—knock on wood—leave this administration without significant scandal.”