The first shows to reopen face a challenge: It is hard to draw audiences without tourists, but hard to draw tourists without shows.LAS VEGAS — Penn Jillette, one half of the Penn & Teller magic and comedy act that has helped define nightlife in Las Vegas for decades, bounded onto the stage the other night and looked across a maskless but socially distanced audience scattered across the theater at the Rio All-Suite Hotel & Casino.“We just did 421 days without a live show,” he said, referring to the forced sabbatical that stretched through the end of April, his silent partner, Teller, finally back at his side. “Boy, it’s nice to see people in the theater.”The next morning, less than a mile away, a troupe of acrobats from Cirque du Soleil was somersaulting through the air, all wearing masks, as they warmed up on a steel frame ship swinging over a 1.2 million-gallon pool in anticipation of reopening “O” in July and a second show, “Mystère,” later this month. By the end of the year they hope to have seven Cirque du Soleil shows back at full capacity.Fifteen months ago, this bustling tourist destination in the desert shut down almost overnight, as theaters, restaurants and casinos emptied out and Las Vegas confronted one of the biggest economic threats in its history. The stakes could not be higher as the Strip tries to emerge from the shadow of the pandemic and the first crop of shows face a challenging reality: It is hard to open shows without tourists, and it’s hard to draw tourist without shows.But a walk through its bustling sidewalks last week suggests an explosion of activity, befitting — in its extravagance, and this city’s appetite for risk — what has always made Las Vegas what it is. The change since last spring, as measured by the return of surging morning-to-midnight crowds, is head-snapping. While just 106,900 tourists visited Las Vegas in April 2020, according to the Convention and Visitors Authority, some 2.6 million people visited this April — a big rebound, but still almost a million shy of what the city was attracting before the pandemic.Penn & Teller recently performed for 250 people scattered around its 1,475-person auditorium. But with restrictions easing, they are increasing capacity — and plan to play to full houses by the end of summer.Joe Buglewicz for The New York Times“You’re in a town that was very irresponsible before,” Jillette said in an interview, remarking on the exuberance of the reopening. “Not the residents, but the people who come to visit Vegas. People who don’t smoke cigars, smoke cigars. People who don’t drink martinis, drink martinis. People who don’t have irresponsible sex, have irresponsible sex. They are proud of it.”Las Vegas began filling its theaters ahead of New York, where most Broadway shows will not reopen until September, and other cities, though many are now rushing to catch up. “I don’t know if culturally that’s a good thing,” Jillette said. “But I will tell you I believe we’re right this time.”The city’s tourism-powered economy was staggered during the pandemic, as Americans avoided airplanes, restaurants, theaters and crowds. Those days seem to be over.“As soon as the governor and the county said we could open, the resorts wanted us to open,” said Ross Mollison, the producer of “Absinthe,” a cabaret and adult humor show, whose website reassures guests by saying, “When you arrive at Absinthe, the Green Fairy promises you filthy fun in a spotless venue.” Penn & Teller had their first Las Vegas show in 1993, and have performed at the Rio since 2001.Joe Buglewicz for The New York TimesPenn & Teller started slowly, as they reunited an act whose first Las Vegas show began in 1993, in deference to the wishes of its performers as well as to state and local health regulations. Their first show was April 22, after both men were vaccinated. By last week 250 people were scattered around its 1,475-person auditorium as the lights dimmed one night just after 9 p.m. But with Nevada Covid-19 restrictions lifted as of June 1 by order of the governor, Steve Sisolak, the show is moving to increase capacity: It plans to sell every seat by the end of the summer, said Glenn S. Alai, its producer.They are at the front of a parade. David Copperfield is up and running, as is “Absinthe,” the Australian Bee Gees, Rich Little and a Prince tribute show. A six-show residency by Bruno Mars at Park MGM in July is sold out, and Usher, Miley Cyrus, Donny Osmond, Barry Manilow, Dave Chappelle, Garth Brooks and Bill Maher are all coming to town. Star D.J.s have been lined up by the city’s mega clubs.A dress rehearsal of “O” by Cirque du Soleil at the Bellagio Hotel & Casino. Performances begin on July 1.Joe Buglewicz for The New York TimesShow business has always been big business in Las Vegas, but it has become even more vital in the decades since the region lost its near-monopoly on legal casino gambling. Before the pandemic, there were more than 100 theaters in Las Vegas, with a combined 122,000 seats, plus 18 arenas that can hold another 400,000 people.About half of the 42 million people who come to Las Vegas in a typical year attend a show, said Steve D. Hill, the president of the Las Vegas Convention and Visitors Authority. “It’s a huge draw, it’s a huge part of the city,” he said. “It’s part of what creates the energy of this place.”Ana Olivier, a designer, and her husband, Van Zyl van Vuuren, a data scientist, bought tickets to four shows when they came here from Atlanta for a week’s long vacation.“Honestly, we just want to get out of the house,” Olivier said as they waited to enter Penn & Teller.Las Vegas is marking this moment with characteristic excess: A fireworks display will light up a long stretch of Las Vegas Boulevard on Independence Day, a coordinated display (produced by Grucci, of course) choreographed off the roofs of seven casinos.Cirque du Soleil hopes to have seven shows running in Las Vegas at full capacity by the end of the year. Performers warmed up for a rehearsal.Joe Buglewicz for The New York TimesThe more cautious approach being taken by most Broadway producers reflects the differences between the two cultures. Broadway theaters tend to be older and smaller, with cramped lobbies, bars, bathrooms and seats. As a matter of pure economics, it is not feasible to socially distance and sell enough seats to cover costs.Theaters in Las Vegas are typically vast and roomy, built into sprawling casino complexes.The pressure to reopen them, from business and political leaders, was huge. Shows are powerful revenue drivers for casinos, not only from box office receipts but for the way they attract tourists and typically require customers to wander through a tempting maze of slot machines, gaming tables, restaurants and bars to find their way to the entrance of the theater.For many shows it has been a slow climb to reopening, as they navigated changing regulations and gauged the eagerness of crowds to return. “Absinthe” tried opening in October, but as it was only allowed to sell a small fraction of its 700 seats, it soon shut down again: Producers decided it was not economically feasible for a show with a large cast and crew. It reopened again in April when it was allowed to increase capacity.Cirque du Soleil performers had to be fitted for costumes and wigs that had been sitting untouched for more than a year.Joe Buglewicz for The New York TimesFor all the optimism in the air, there are still reminders that this remains a moment of uncertainty. Performers, crew members and visitors to “O” rehearsals were required to get coronavirus tests to enter the theater. Performers wore masks even as they did their midair acrobatics, or went to subterranean dressing rooms to try on costumes and wigs that had been sitting untouched for more than a year. (The mask requirement was waved for swimmers and scuba divers.)Penn & Teller have had to make adjustments. They no longer rush to the door to shake hands with fans as they leave, a tradition for 45 years. And now, when they seek volunteers from the audience to come onstage, they relegate them to a chair at the end of the stage, well away from Jillette or Teller.The rehearse-in-masks requirement was waived for one set of Cirque du Soleil performers: its swimmers.Joe Buglewicz for The New York Times“You won’t find me strolling around in a supermarket without a mask for a while,” Teller said in an interview. “I am going to stick with the most careful protocols that are around. We are dying to have people onstage. Obviously we are not going to jump into that until we are confident that is the safe thing to do.”Signs posted in casinos announce that vaccinated people do not need to wear masks, but that those who have not been vaccinated must cover their mouths — not that there are enforcers walking around the casino floors demanding C.D.C. vaccination cards. That means that “O” cast and crew walk out of the high-precaution Covid-is-still-with-us environment of their theater and into the decidedly laxer world of the rest of Las Vegas.The travel and leisure audience alone will not be enough to assure that entertainment in Las Vegas can return to what it was. The key question now is whether convention business returns after the Zoom era. Alan Feldman, a fellow at the International Gaming Institute at the University of Nevada, Las Vegas, said that was what he was watching most closely, although he said the rising interest in tourism was a good sign. “There is clearly pent-up demand for Las Vegas,” he said.Tourists are coming back, if not yet at pre-pandemic levels. The next question is whether the convention business will rebound after an era where remote meetings flourished.Joe Buglewicz for The New York TimesProducers, having weathered what most described as the most difficult time of their careers, are hopeful that in the weeks ahead, Las Vegas will show the world that it is safe to return to something close to business as usual.“I am very confident,” said Daniel Lamarre, the president of Cirque du Soleil. “We are selling at a pace that is double what we do normally. It indicates to me that people are just crazy to go out and see humans perform. ”Tourists make up the overwhelming majority of people who come to the Strip, but some Las Vegas area residents venture out as well. John Vornsand, a retired Clark County planner who lives in nearby Henderson, had not seen a show here since Rod Stewart performed in 2019 at Caesars Palace. He was back the other night with his wife, Karen, for Penn & Teller.“I bought the tickets the first day they were out,” said Vornsand, who is vaccinated. “I said, ‘It’s her birthday and that’s it.’”“We don’t feel uncomfortable,” he said. “Although I do have a mask in my pocket.” More