WASHINGTON — In a White House populated by aides who have flamed out, lashed out or cashed out — some do all three in the same day — Hope Hicks, the administration’s communications director, has maintained a low profile as an influential adviser of a mercurial president who prizes her loyalty.

On Friday, President Trump publicly returned the favor.

A day after the departure of Rob Porter, a White House aide who resigned amid domestic abuse accusations, the president dismissed an idea circulated by some aides and allies that he had been unhappy with Ms. Hicks’ role in workshopping an initial forceful defense of Mr. Porter. Ms. Hicks had been dating Mr. Porter until recently.

“Hope is absolutely fantastic,” Mr. Trump said in a statement released through a spokesman. “She was with the campaign from the beginning, and I could not ask for anything more. Hope is smart, very talented and respected by all.”

Ms. Hicks did not know about the specific allegations made against Mr. Porter until Tuesday, according to a White House official. That day, she met with other White House officials in drafting the initial statements sent in Mr. Porter’s defense, according to two West Wing officials.

Rumblings began about the president’s unhappiness with a haphazard situation handled without his knowledge, and Mr. Trump spent Thursday working the phones, referring to Mr. Porter in one call as “bad garbage” and saying that he questioned Ms. Hicks’s judgment, according to two advisers.

But while questions continue to swirl about whether Mr. Kelly will survive the scandal — he offered to resign on Friday — in Ms. Hicks’ case the West Wing trotted out a host of senior officials to defend her. On Friday the lineup included Ivanka Trump, the president’s daughter and senior adviser, and Steven Mnuchin, the Treasury secretary.

“I have been impressed with Hope since I started working with her on the campaign,” Mr. Mnuchin said in a statement that was volunteered by an aide. “She is exceptionally talented in leading communications for the administration. I view her as an invaluable asset to the president and us all.”

Ms. Trump, who hired Ms. Hicks several years ago to work for her company before Ms. Hicks was tapped to serve on the Trump campaign in 2015, said Ms. Hicks was a “team player” who’d earned the president’s confidence.

“Most importantly,” Ms. Trump said in an unsolicited interview, “the president has deep respect for her, cares about her greatly, and listens to her. That’s not true of everyone. She’s earned that.”

Ms. Hicks, a 29-year-old former model, brought an aggressive, corporate-world training to the world of politics. With a background in defending the client against all threats — and, if necessary, all odds — she earned Mr. Trump’s trust during the campaign.

The bond grew as Mr. Trump ascended to the White House and was suddenly surrounded by a sea of unfamiliar faces. Ms. Hicks has been a constant at his side on trips and photo opportunities, and keeps as close an eye as possible on Mr. Trump’s interviews with journalists.

In their years together, Ms. Hicks has helped write pugilistic statements on Mr. Trump’s behalf, including one that delivered a blow to Stephen K. Bannon, the president’s former chief strategist: “Steve pretends to be at war with the media, which he calls the opposition party, yet he spent his time at the White House leaking false information to the media to make himself seem far more important than he was,” that statement read.

During the campaign, Ms. Hicks also stepped forward to defend Corey Lewandowski, Mr. Trump’s onetime campaign manager. She said Mr. Lewandowski had “nothing to apologize for” after he grabbed a reporter who later filed battery charges against him.

“I think the president always likes somebody who looks like they’re out of central casting,” Chris Ruddy, the chief executive of Newsmax Media and a friend of the president, said in an interview. “But he does want people to know what they’re doing. He also puts a high value on loyalty. And she’s been extremely loyal.”

For the last several months, Ms. Hicks and Mr. Porter have been seen around Washington, attending group dinners together. One person close to Ms. Hicks, who spoke on condition of anonymity out of loyalty to her, said Mr. Porter had made his way into the small circle of people she felt she could trust after several years in an often chaotic work environment.

On Friday aides throughout the West Wing were still struggling to reconcile Mr. Porter’s accused private behavior with the person they knew at work, according to a senior administration official.

But in the Oval Office, Ms. Hicks was there as Mr. Trump offered praise and support for Mr. Porter.

“We absolutely wish him well,” the president said, as Ms. Hicks stood nearby.

Maggie Haberman contributed reporting.

A version of this article appears in print on , on Page A15 of the New York edition with the headline: At Demanding Workplace, Aide Is Singled Out as ‘Absolutely Fantastic’. Order Reprints | Today’s Paper | Subscribe