“There’s more wheeling and dealing,” Mr. Nuschese said.
Originally from Minori, Italy, Mr. Nuschese, 56, learned the importance of discretion while managing restaurants in Las Vegas, another city where luck can change in an instant. As a policy, he will not publicly say who visits, but in an era where today’s lunch becomes tomorrow’s e-newsletter gossip tidbit, news has a way of leaking quickly. The evening after Mr. Mnuchin dined at the restaurant, sipping red wine with his back to the wall, Secretary of State Rex W. Tillerson shared dinner and red wine in a private room with Senator Mark Warner, Democrat of Virginia. Wilbur L. Ross, the commerce secretary, has also been spotted among the tables. Reporters often call the restaurant within minutes, trying to confirm the sightings.
Mr. Trump has so far not visited, but members of his Republican administration may be heading here because it is insulated from the opposition. Even in a neighborhood where local establishments are known to host Make Georgetown Great Again parties, running into angry residents of this heavily Democratic city is a reality: Just around the corner, Sean Spicer, the White House press secretary, was recently accosted at the Georgetown Apple store.
Newt Gingrich, the former House speaker, said in an interview that members of the administration might be seeking out a place to relax.
“I saw Rex Tillerson there one night after he had been through Senate hearings,” Mr. Gingrich said. “He wanted to go there with his family and take off his tie.”
It’s also possible, Mr. Gingrich said, that the Washington establishment’s newest arrivals are just getting the lay of the land.
“Washington changes with each party,” he said. “But they say to the newcomers, ‘Do you want to go to Cafe Milano?’”
Representative Debbie Dingell, Democrat of Michigan and a longtime fixture of Washington’s social scene, suggested that bipartisan behavior can sometimes rise above the fray at this establishment.
“If you have a relationship with someone,” she said, “it’s much harder to demonize them.”
If the new secretary of state feels comfortable dining observed but unbothered with a Democrat at Cafe Milano, it is because Mr. Nuschese keeps order. Along with the regular presence of Secret Service details, several men in gray suits scan the restaurant during the dinner hour, their hands clasped, watching like hawks for signs of dining discomfort, be it cold fish, interlopers or threats. (The restaurant was the target of a bomb plot to assassinate Adel al-Jubeir, then the Saudi ambassador, in 2011.) It’s not uncommon to see one of these employees whisper in Mr. Nuschese’s ear or slip a piece of folded paper toward his lunch plate.
Gauche behavior is punished. Once, after Mr. Nuschese caught a woman from a rival Italian restaurant — he would not publicly say which one — passing out business cards, he had one of his employees slip the woman one from his private stash. It read: “The management requests you leave quietly.”
Peace of mind is what Mr. Nuschese is selling.
“In Washington, you need to have that level of trust among all of us,” he said. “The minute they walk inside, the door closes right there.”
Mr. Nuschese said he was annoyed by “spies” who breach the restaurant’s privacy rules: After Mr. Tillerson dined with Mr. Warner late last month, a source quickly relayed the information to The Washington Post. Still, as sightings documented by gossip columnists or in e-newsletters like Politico Playbook grow more frequent, he keeps up on the coverage.
“A bottle of red wine on the table?” Mr. Nuschese said, exasperated by a detail that slipped out about Mr. Tillerson’s meeting. “I was like, ‘Oh my God.’”
Mr. Nuschese’s friends say he is as much a fixture of Washington as the people he hosts. He has teamed up with vineyards in Italy to create a wine company, Capital Wines. (“A little bit pricey,” Mr. Gingrich said.) Mr. Nuschese hosted an 81st birthday lunch for Benedict XVI, the pope emeritus. He sends his friends flowers on their wedding anniversaries. And he puts on big parties. At his home in the Forest Hills neighborhood, which he bought for around $3.5 million in 2002, he has hosted events that draw hundreds. A party that featured $50 million worth of baubles supplied by the Italian jeweler Bulgari was among the most extravagant. An oil painting of Pope John Paul II sits in his dining room, a gift from the Vatican.
“He’s really human,” said Ms. Dingell, who receives anniversary flowers from him each year.
Another friend, the journalist Charlie Rose, called Mr. Nuschese a “master” of creating a comfortable atmosphere.
The restaurant draws both Republicans and Democrats. High-ranking members of President Barack Obama’s administration also frequented Cafe Milano — Valerie Jarrett is known to be a regular, and the Obamas visited several times.
The CNN anchor Wolf Blitzer has covered several presidential administrations and has been coming to Cafe Milano regularly for two decades. He said the Trump team was avidly going out.
“A lot of the cabinet secretaries are not just finishing the day and going home,” Mr. Blitzer said. “I think from their perspective it’s probably part of their job to go out and work their various contacts.”
When it comes to contacts, Mr. Nuschese has so many that he travels with three BlackBerrys: One is for American business, another for his ventures in Italy and the third for the Middle East. He recently opened a Cafe Milano outpost in the Four Seasons in Abu Dhabi and travels there once a month. It is, he said, a joint venture with the government.
Yousef al-Otaiba, the ambassador from the United Arab Emirates, is another frequent visitor. In an email, Mr. Otaiba said he expected Mr. Nuschese would use his Washington “recipe” to make the new restaurant a success. That recipe, according to Mr. Nuschese and those who know him, is to continue keeping his high-profile customers comfortable.
Any criticism about those relationships becoming too cozy doesn’t seem to bother him.
“Obviously,” Mr. Nuschese said, “the clientele that comes, they don’t think this is a swamp.”