"She hears footsteps from above, shuffling against the attic floorboards. A framed painting suddenly vanishes from a wall. The gas-fueled flames of the chandelier flicker and dim.
She is certain it happened — but her husband assures her that she’s imagining it all. It’s her behavior that seems odd, he insists; perhaps she’s going mad? And, slowly, she begins to believe him.
This is the plot of the 1944 Ingrid Bergman film “Gaslight.” It is also the origin of a buzzword that has spread from pop culture to clinical psychology and back again — but has never been more visible than it is now, in commentary about the conduct of President Trump:
CNN: Donald Trump is ‘gaslighting’ all of us
Teen Vogue: Donald Trump Is Gaslighting America
NBC: Some Experts Say Trump Team’s Falsehoods Are Classic ‘Gaslighting’
This is a very specific accusation. To “gaslight” someone isn’t just to lie to them or to manipulate their emotions. It is a deliberate attempt to deceive someone into questioning their own perception of reality. (“Suddenly, I’m beginning not to trust my memory at all,” says Bergman’s character, Paula, as her faith in her senses begins to fray.)
Throughout Trump’s ascent to the presidency, he was repeatedly accused of this sort of manipulation. When he wanted to shift attention away from his vocal support of the birther movement, he falsely claimed that Hillary Clinton had started the conspiracy theory. Trump told the New York Times that it was a “mistake” for him to retweet an unflattering photo of Ted Cruz’s wife — then later insisted in a TV interview, “I didn’t actually say it that way.” He vehemently denied that he had mocked a disabled reporter, despite a widely circulated video that showed him doing exactly that. After winning the election by a narrow margin, losing the popular vote by nearly 3 million, Trump hailed his victory as a “landslide.” Most recently, Trump and his administration have insisted that the crowd at his inauguration was the largest in American history — even as aerial photographs, crowd estimates, Metro ridership numbers and witnesses on the scene show otherwise." WP
https://en.wikipedia.org/wiki/Gaslighting