Republican presidential candidate Donald Trump speaks to the media after the GOP debate in Houston. (Joe Raedle/Getty Images)

AS DONALD Trump’s presidential campaign gathers momentum, some people who initially were repelled by the prospect are reassuring themselves that the nation could easily survive his presidency. He’s a dealmaker and a pragmatist, they say. He doesn’t really believe the hateful messages he’s been spewing to win votes. He will be tamed by the American system of checks and balances.

Comments Mr. Trump delivered on Friday should shake that complacency. His remarks about using government to attack companies and newspapers he doesn’t like, and to change libel law so that he can shut down criticism in the press, are genuinely un-American. They reflect an attitude toward using government power to target opponents that would be entirely familiar to people who live in Vladi­mir Putin’s Russia or Chavista Venezuela. They have had no currency in Washington since the darkest, most paranoid days of Richard Nixon’s enemies list.

Mr. Trump directed his venom toward the New York Times, which he called “dishonest” and “the absolute worst,” and to The Post and its owner, Amazon founder and chief executive Jeffrey P. Bezos. “I have to tell you, I have respect for Jeff Bezos, but he bought The Washington Post to have political influence,” Mr. Trump said. “He wants political influence so that Amazon will benefit from it. That’s not right. And believe me, if I become president, oh, do they have problems. They’re going to have such problems.”

As it happens, Mr. Trump was inaccurate in his assertion, as he is in so many of his statements. Mr. Bezos has made clear publicly that he has no desire to use The Post for political ends, and he has chosen to exercise no influence over editorial decisions. However, as the owner, he’d be fully entitled to chart its ideological course if he wanted to, just as the owners of the Times, the Wall Street Journal and other great American newspapers do and have done for decades. The beauty of the American system is that it is a marketplace of ideas. News outlets compete for readers and viewers — not for government favor.

Mr. Trump went on to say that as president he would “open up the libel laws, so when they write purposefully negative and horrible and false articles, we can sue them and win lots of money.” In fact, current law already allows public figures to sue for damages if the media write “purposefully” false allegations. But the law makes public figures work harder to prove media recklessness than private citizens, who don’t have to prove that a falsehood was malicious or intentional. That difference, established by the Supreme Court more than a half century ago, has helped ensure the kind of lively political debate that Mr. Trump enjoys — except, apparently, when he is on the receiving end.

Is Mr. Trump a threat to democracy? In history, it has generally been a mistake to laugh off the words of would-be dictators as they climbed to power. “If I become president, oh, do they have problems,” Mr. Trump says. If he acts on his threats, none of us will be able to say we received no warning.