Ms. Trump’s announcement this past week that she would shut down her fashion brand, based in New York, seemed to symbolize a recommitment to her life and her husband’s in Washington. The woman who once said that she did not intend to stay in the capital long enough to become one of its “political creatures” — people she feels are “so principled that they get nothing done,” according to someone familiar with her thinking — said on Tuesday that she did not know “if I will ever return to the business.”

“Any suggestion that they were going to leave the White House was just ridiculous,” said Steven Mnuchin, the Treasury secretary, who was one of several allies the couple asked to speak on their behalf for this article. “They both have been dependable, valuable and effective partners for me and other members of the president’s cabinet.”

Although they have kept a foothold in Manhattan, home is now in Washington, where their children attend Jewish schools and their house is routinely watched by paparazzi as they depart for work or go for a run. They live in a rented mansion in the Kalorama neighborhood, where they have courted groups of lawmakers and Washington hands in an effort to ease hyperpartisan tensions over cocktails and comfort food.

Their allies say this is a sign that the two, both children of businessmen, have adjusted to the market. But intentionally or not, Mr. Kushner and Ms. Trump have redefined the expectations that people in their New York social circle once had that the two would be horrified by the president’s policies and change them.

“I never counted on it, but they themselves promoted the idea that they would save us,” said Hilary Rosen, a Democratic strategist who has been a vocal critic of the administration, before ticking off a list of policies that Mr. Trump has sought to dismantle.

As for separating immigrant families, she added, “How do they sleep at night?”

In response to critics like Ms. Rosen, the couple have argued that they can temper Mr. Trump only if he is willing to listen. And sometimes he has been: Ms. Trump pushed for the expanded child tax credit in the tax cut bill that passed in 2017, and Mr. Kushner has convinced the president that criminal justice reform is worthwhile, even as his attorney general remains a vocal opponent.