It’s a Saturday evening, time for mere mortals to kick back. But not Plácido Domingo. The world’s most famous tenor has just flown in from New York to work into the night with young singers from the Washington National Opera.

There’s some Mozart from a local soprano, a Ukrainian baritone, and an ensemble that includes a singer who is German-born but educated in Arkansas. There’s Donizetti from a Mexican-born tenor who has served with the US Army in Iraq. There’s some Gounod from another Mexican-born tenor who left law school and a job at Wal-Mart headquarters for a shot at a career like Domingo’s.

The object is far beyond getting tempos or the interpretation of a role correct. The bigger point is to see if, under Domingo’s tutelage, lightning will strike one of the budding artists. The scene in the Kennedy Center rehearsal hall feels like the passing of the torch from a legendary figure to a new generation.

As the Metropolitan Opera program put it earlier this season: “Plácido Domingo is a phenomenon.” And his exceptionalism looms larger for Washington than for any other city in the world—a world in which Domingo, at 68, is one of classical music’s most enduring stars.

As a director of the Washington National Opera since 1996 as well as a sometime performer and conductor with the company, Domingo is the most important musical force in town. His position is so significant that it unnerves the city’s cultural establishment to think about what could happen when Domingo’s contract runs out in 2011.

“I think everyone kind of hopes it will go on forever,” says Selwa “Lucky” Roosevelt, secretary of the opera’s board and a pivotal figure in the private negotiations that brought Domingo to run the opera. That marked a new day for the arts here. “Everyone assumed that Washington was no longer a desert,” she says.

Domingo is more self-deprecating but concedes, “When I came, it was time to grow . . . time to develop. . . . And indeed we have grown.”

What worries Roosevelt and other opera enthusiasts is that over the 13 years of Domingo’s tenure, “we’ve all come to sort of take it for granted.”

Local classical-music lovers in general and opera devotees in particular have pinched themselves at the city’s luck in hooking Domingo and keeping him here for so long. They’d better now reach for their checkbooks. If there is a cautionary note to Domingo’s Washington tenure, it is that artistic advances have been accompanied by bigger budgets, with the opera struggling to stay in the black—and sometimes not succeeding.

“I was sure the budget would go up, and it has,” says Roosevelt, a prodigious opera fundraiser. Domingo concedes the point rather proudly even as he acknowledges straitened times for all the arts amid the international economic crisis.

WNO expenses and contributions have almost doubled since 1997, Domingo’s first full year as chief of the company. But earned revenue, principally from ticket sales, has been virtually flat, in part because attendance was already good and because the Opera House has fewer seats than venues in New York, Chicago, San Francisco, and Los Angeles, where Domingo is also general director of LA Opera. That means there is less room for WNO’s revenue to grow and more pressure on fundraising.

Domingo has proven to be a money magnet, but he’s not a miracle worker—especially in an economy that already has seen two US opera companies, including one in Baltimore, effectively close and even the mighty Metropolitan in New York tighten its belt. WNO announced in November the indefinite postponement of three cycles of Wagner’s four-part masterpiece, Der Ring des Nibelungen, originally scheduled for later this year, for which planning began seven years ago.

“Without any doubt, we need new blood,” Domingo says. As at almost every opera company, the most generous donors are older and their places need to be filled by younger contributors.

WNO ran up what the company calls an accumulated unrestricted deficit of $19.8 million through fiscal 2007 that still hangs over the company. Executive director Mark Weinstein, brought in a year ago to sort out the company’s finances, says WNO balanced its books last year and expects to in the current fiscal year, which ends June 30. Domingo counts that almost a miracle in this economic climate.

“The financial challenges are major,” says Kenneth Feinberg, a veteran Washington lawyer who is president of WNO’s board of trustees. “Can we meld Plácido’s vision with economic realities?”

Domingo says he was urging even before the global financial crisis that “if we want to go at this speed, we need $5 million more” annually. Given the downturn, he believes it would take an additional $8 million annually to “make it really comfy.”

Domingo, who has sung for popes, prays for an angel who will wipe out the red ink: “My really biggest, biggest, biggest dream is that one person that can really afford it will say, hey, here it is, for the deficit. . . . To pay the deficit it means the biggest vitamin injection that you can give to the company.” Wiping out an accumulated shortfall is “the most difficult thing,” Domingo says, because big-time donors would rather pay for a new production than cover losses from past seasons.

Says a company insider who praises Domingo while wondering about WNO’s ability to keep up financially, “It’s a real stretch.” But continuing the stretch may be key to keeping Domingo.