After the publication of an anonymous op-ed by about the “resistance” against President Donald Trump‘s “worst inclinations” from within the administration, a frantic search for the identity of the anonymous official has started.

The New York Times op-ed came from an unnamed author identified as a “senior official in the Trump administration” who claimed to be a part of a group of administration officials working to combat Trump’s agenda. The blistering piece detailed how officials floated the idea of using the 25th Amendment to the Constitution to remove Trump from office and referred to the “great lengths” administration staffers have gone to “keep bad decisions contained to the West Wing.”

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In the president’s initial response to the op-ed, Trump called for the Times to reveal the name of the administration official. He called in tweets on Wednesday the person “GUTLESS” and starkly asked for “TREASON?”

White House Press Secretary Sarah Sanders said in a statement that the author should resign, calling him a “coward.”

“The individual behind this piece has chosen to deceive, rather than support, the duly elected president of the United States,” she said. “He is not putting country first, but putting himself and his ego ahead of the will of the American people. This coward should do the right thing and resign.”

“It is not mine,” Mike Pompeo, the secretary of State, said of the piece during brief remarks in India on Thursday, according to the Times. Also Vice President Mike Pence‘s office denied to be the author of the op-ed.

Some of Trump’s 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. His ire was trained particularly on two former aides, the former director of the National Economic Council, Gary  Cohn, and the former staff secretary, Rob Porter, according to people close to the White House.