Mr. Spicer tossed off his share of falsehoods (a dubious claim about crowd size comes to mind), but he could never quite conceal the strain of life as President Trump’s press secretary. The fear of a mercurial boss, the constant pressure to misdirect — it played out on live TV across his face, a grimace that gave the game away.

Ms. Sanders, who announced her departure on Thursday, never seemed especially flustered.

“It’s one of the greatest jobs I could ever have; I’ve loved every minute, even the hard minutes,” she said at the White House, after Mr. Trump praised her and gave her a kiss on the head.

In contrast to Mr. Spicer’s flop-sweat demeanor, Ms. Sanders displayed the devotion of a true believer. “God calls all of us to fill different roles at different times, and I think that he wanted Donald Trump to become president,” Ms. Sanders, an evangelical who prayed before her briefings, told the Christian Broadcasting Network.

In an interview with The New York Times shortly after taking her job, she confessed that she “certainly didn’t approve” of some of Mr. Trump’s remarks on the campaign trail.

“But at the same time, we were looking for a commander in chief,” she added. “Not a pastor.”

The first mother to serve as press secretary, Ms. Sanders was feted upon her promotion by female reporters and White House aides at a “women of the White House” happy hour. She could be sociable with reporters, sipping wine after hours and offering guidance behind closed West Wing doors.