Update, Feb. 28, 2018: Hope Hicks announced that she was resigning as White House communications director. For the latest updates and further coverage, read here.

An inspirational poster hangs above the Trump Tower desk of Hope Hicks, the 27-year-old press secretary for Donald J. Trump’s presidential campaign, squeezed in among the framed Time magazine covers of Mr. Trump and exuberant thank-you notes written in his inimitable scrawl (“Hopie — You’re the greatest!”).

“Fate whispers to the warrior, ‘You cannot withstand the storm,’” it reads. “And the warrior whispers back, ‘I am the storm.’”

Ms. Hicks, a onetime champion lacrosse player who signed a Ford modeling contract as a teenager, had never worked in politics before last year, and her widest exposure had been as a co-star in a Nickelodeon children’s television special about golf.