WASHINGTON — Stephanie Grisham doled out fast food and tracked lost gear as a press wrangler on President Trump’s 2016 campaign, far from the in-crowd flying on the gold-plated Trump jet. An early and hard-working convert to Mr. Trump’s cause, she told a reporter at one point that she was “riding it until the money runs out,” eager to return home to Arizona.

Instead, Ms. Grisham, 43, rode all the way to Washington with Mr. Trump. And now, after serving in the press office and as Melania Trump’s spokeswoman, she occupies one of the most prestigious roles in American politics, as White House press secretary and communications director for both the president and the first lady.

For a public relations specialist who once churned out news releases on traffic safety, the White House is the loftiest stop in a turbulent career trajectory that has mixed toughness and loyalty to her bosses with professional scrapes, ethical blunders and years spent alternately wooing and pounding the press on behalf of scandal-prone Arizona Republicans.

“I’ve always had a picture of the White House and it would always sit right in front of my desk” in the Arizona Capitol, Ms. Grisham told a local television interviewer from the state shortly after joining the administration. “Whenever I was having a hard day I could look at it and remember what my goal was.”