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An anonymous op-ed appears to have rattled Trump.

The president is not laughing off an unsigned critique of his presidency allegedly written by a senior administration official which was published by The New York Times on Wednesday.

Trump has responded with four angry tweets:

Trump’s press secretary, Sarah Huckabee Sanders, echoed many of these points in her own statement. “Nearly 62 million people voted for President Donald J. Trump n 2016, earning him 306 electoral college votes—versus 232 for his opponent,” Sanders claimed (strangely understating Trump’s victory of nearly 63 million votes). “None of them voted for a gutless, anonymous source to the failing New York Times.”

The New York Times reports that the combined impact of the new Bob Woodward expose with the anonymous op-ed is starting to unnerve the president: “Mr. Trump’s mood vacillated from fury to calm throughout Tuesday afternoon and Wednesday. Some of his top aides worked the phones to figure out who was leaking or who might have spoken, and his daughter Ivanka Trump and other advisers tried to quell his distress.”