On May 17th, a black-tie audience at the Metropolitan Opera House applauded as a tall, jovial-looking billionaire took the stage. It was the seventieth annual spring gala of American Ballet Theatre, and David H. Koch was being celebrated for his generosity as a member of the board of trustees; he had recently donated $2.5 million toward the company’s upcoming season, and had given many millions before that. Koch received an award while flanked by two of the gala’s co-chairs, Blaine Trump, in a peach-colored gown, and Caroline Kennedy Schlossberg, in emerald green. Kennedy’s mother, Jacqueline Kennedy Onassis, had been a patron of the ballet and, coincidentally, the previous owner of a Fifth Avenue apartment that Koch had bought, in 1995, and then sold, eleven years later, for thirty-two million dollars, having found it too small.

The gala marked the social ascent of Koch, who, at the age of seventy, has become one of the city’s most prominent philanthropists. In 2008, he donated a hundred million dollars to modernize Lincoln Center’s New York State Theatre building, which now bears his name. He has given twenty million to the American Museum of Natural History, whose dinosaur wing is named for him. This spring, after noticing the decrepit state of the fountains outside the Metropolitan Museum of Art, Koch pledged at least ten million dollars for their renovation. He is a trustee of the museum, perhaps the most coveted social prize in the city, and serves on the board of Memorial Sloan-Kettering Cancer Center, where, after he donated more than forty million dollars, an endowed chair and a research center were named for him.

One dignitary was conspicuously absent from the gala: the event’s third honorary co-chair, Michelle Obama. Her office said that a scheduling conflict had prevented her from attending. Yet had the First Lady shared the stage with Koch it might have created an awkward tableau. In Washington, Koch is best known as part of a family that has repeatedly funded stealth attacks on the federal government, and on the Obama Administration in particular.

With his brother Charles, who is seventy-four, David Koch owns virtually all of Koch Industries, a conglomerate, headquartered in Wichita, Kansas, whose annual revenues are estimated to be a hundred billion dollars. The company has grown spectacularly since their father, Fred, died, in 1967, and the brothers took charge. The Kochs operate oil refineries in Alaska, Texas, and Minnesota, and control some four thousand miles of pipeline. Koch Industries owns Brawny paper towels, Dixie cups, Georgia-Pacific lumber, Stainmaster carpet, and Lycra, among other products. Forbes ranks it as the second-largest private company in the country, after Cargill, and its consistent profitability has made David and Charles Koch—who, years ago, bought out two other brothers—among the richest men in America. Their combined fortune of thirty-five billion dollars is exceeded only by those of Bill Gates and Warren Buffett.

The Kochs are longtime libertarians who believe in drastically lower personal and corporate taxes, minimal social services for the needy, and much less oversight of industry—especially environmental regulation. These views dovetail with the brothers’ corporate interests. In a study released this spring, the University of Massachusetts at Amherst’s Political Economy Research Institute named Koch Industries one of the top ten air polluters in the United States. And Greenpeace issued a report identifying the company as a “kingpin of climate science denial.” The report showed that, from 2005 to 2008, the Kochs vastly outdid ExxonMobil in giving money to organizations fighting legislation related to climate change, underwriting a huge network of foundations, think tanks, and political front groups. Indeed, the brothers have funded opposition campaigns against so many Obama Administration policies—from health-care reform to the economic-stimulus program—that, in political circles, their ideological network is known as the Kochtopus.

In a statement, Koch Industries said that the Greenpeace report “distorts the environmental record of our companies.” And David Koch, in a recent, admiring article about him in New York, protested that the “radical press” had turned his family into “whipping boys,” and had exaggerated its influence on American politics. But Charles Lewis, the founder of the Center for Public Integrity, a nonpartisan watchdog group, said, “The Kochs are on a whole different level. There’s no one else who has spent this much money. The sheer dimension of it is what sets them apart. They have a pattern of lawbreaking, political manipulation, and obfuscation. I’ve been in Washington since Watergate, and I’ve never seen anything like it. They are the Standard Oil of our times.”

A few weeks after the Lincoln Center gala, the advocacy wing of the Americans for Prosperity Foundation—an organization that David Koch started, in 2004—held a different kind of gathering. Over the July 4th weekend, a summit called Texas Defending the American Dream took place in a chilly hotel ballroom in Austin. Though Koch freely promotes his philanthropic ventures, he did not attend the summit, and his name was not in evidence. And on this occasion the audience was roused not by a dance performance but by a series of speakers denouncing President Barack Obama. Peggy Venable, the organizer of the summit, warned that Administration officials “have a socialist vision for this country.”

Five hundred people attended the summit, which served, in part, as a training session for Tea Party activists in Texas. An advertisement cast the event as a populist uprising against vested corporate power. “Today, the voices of average Americans are being drowned out by lobbyists and special interests,” it said. “But you can do something about it.” The pitch made no mention of its corporate funders. The White House has expressed frustration that such sponsors have largely eluded public notice. David Axelrod, Obama’s senior adviser, said, “What they don’t say is that, in part, this is a grassroots citizens’ movement brought to you by a bunch of oil billionaires.”

In April, 2009, Melissa Cohlmia, a company spokesperson, denied that the Kochs had direct links to the Tea Party, saying that Americans for Prosperity is “an independent organization and Koch companies do not in any way direct their activities.” Later, she issued a statement: “No funding has been provided by Koch companies, the Koch foundations, or Charles Koch or David Koch specifically to support the tea parties.” David Koch told New York, “I’ve never been to a tea-party event. No one representing the tea party has ever even approached me.”

At the lectern in Austin, however, Venable—a longtime political operative who draws a salary from Americans for Prosperity, and who has worked for Koch-funded political groups since 1994—spoke less warily. “We love what the Tea Parties are doing, because that’s how we’re going to take back America!” she declared, as the crowd cheered. In a subsequent interview, she described herself as an early member of the movement, joking, “I was part of the Tea Party before it was cool!” She explained that the role of Americans for Prosperity was to help “educate” Tea Party activists on policy details, and to give them “next-step training” after their rallies, so that their political energy could be channelled “more effectively.” And she noted that Americans for Prosperity had provided Tea Party activists with lists of elected officials to target. She said of the Kochs, “They’re certainly our people. David’s the chairman of our board. I’ve certainly met with them, and I’m very appreciative of what they do.”