FLASHBACK: If Donald Trump Targets Journalists, Thank Obama.

If Donald J. Trump decides as president to throw a whistle-blower in jail for trying to talk to a reporter, or gets the F.B.I. to spy on a journalist, he will have one man to thank for bequeathing him such expansive power: Barack Obama. . . .

Criticism of Mr. Obama’s stance on press freedom, government transparency and secrecy is hotly disputed by the White House, but many journalism groups say the record is clear. Over the past eight years, the administration has prosecuted nine cases involving whistle-blowers and leakers, compared with only three by all previous administrations combined. It has repeatedly used the Espionage Act, a relic of World War I-era red-baiting, not to prosecute spies but to go after government officials who talked to journalists.

Under Mr. Obama, the Justice Department and the F.B.I. have spied on reporters by monitoring their phone records, labeled one journalist an unindicted co-conspirator in a criminal case for simply doing reporting and issued subpoenas to other reporters to try to force them to reveal their sources and testify in criminal cases. . . .

In a scathing 2013 report for the Committee to Protect Journalists, Leonard Downie, a former executive editor of The Washington Post who now teaches at Arizona State University, said the war on leaks and other efforts to control information was “the most aggressive I’ve seen since the Nixon administration, when I was one of the editors involved in The Washington Post’s investigation of Watergate.”

When Mr. Obama was elected in 2008, press freedom groups had high expectations for the former constitutional law professor, particularly after the press had suffered through eight years of bitter confrontation with the Bush administration. But today, many of those same groups say Mr. Obama’s record of going after both journalists and their sources has set a dangerous precedent that Mr. Trump can easily exploit.

The irresponsibility of the leakers provides him more opportunities. It’s clear that they’re not leaking to expose wrongdoing, but to engage in political warfare.