The response from the city was not initially sympathetic. “I will not tell you that Gucci and Tiffany are my central concerns in life,” Mayor Bill de Blasio said at a news conference held outside of Trump Tower, following a meeting with the president-elect on Nov. 16.

But at a subsequent news conference on Nov. 18, the mayor and the police commissioner, James P. O’Neill, announced their intention to keep Fifth Avenue open, following three temporary closures in the immediate aftermath of the election and the protests that followed.

“We are devoted to making sure the city will keep moving,” Mr. de Blasio said. “This is a big challenge and an unprecedented challenge, we know that. We’re committed to making it work.”

He said that he was “very concerned to make sure that businesses continue to thrive, continue to be able to serve their customers and do well,” but also asked that New Yorkers avoid the area between 53rd and 57th Streets, between Madison Avenue and Avenue of the Americas, “to the maximum extent possible,” a request not likely to please those retailers in this high-priced luxury corridor, where rents can run a reported $5,000 per square foot.

(The commotion has already raised the hackles of the Momofuku restaurateur David Chang, who has tweeted his displeasure at traffic disruptions on 56th Street, where his Má Pêche restaurant is.)

On Fifth Avenue between 56th and 57th alone, there are stores for Abercrombie & Fitch and Prada, as well as the multiunit Crown Building at 730 Fifth Avenue, home to Mikimoto, Piaget and Bulgari. Ermenegildo Zegna plans to open a store there. Jason Maurer, the leasing agent for the property, declined to discuss the building.