Even outside periods of unusual wealth, members of this group generally hover in the $100,000-plus income range, keeping them in the top 20 percent of earners.
Companies increasingly are marketing to this rising demographic, fueling a surge of "mass luxury" products and services from premium Starbucks coffee and organic groceries to concierge medicine and VIP lanes at airports. Political parties are taking a renewed look at the up-for-grabs group, once solidly Republican.
They're not the traditional rich.
In a country where poverty is at a record high, today's new rich are notable for their sense of economic fragility. They've reached the top 2 percent, only to fall below it, in many cases. That makes them much more fiscally conservative than other Americans, polling suggests, and less likely to support public programs, such as food stamps or early public education, to help the disadvantaged.
Last week, President Barack Obama asserted that growing inequality is "the defining challenge of our time," signaling that it will be a major theme for Democrats in next year's elections.
New research suggests that affluent Americans are more numerous than government data depict, encompassing 21 percent of working-age adults for at least a year by the time they turn 60. That proportion has more than doubled since 1979.
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At the same time, an increasing polarization of low-wage work and high-skill jobs has left middle-income careers depleted.
"For many in this group, the American dream is not dead. They have reached affluence for parts of their lives and see it as very attainable, even if the dream has become more elusive for everyone else," says Mark Rank, a professor at Washington University in St. Louis, who calculated numbers on the affluent for a forthcoming book, "Chasing the American Dream," to be published by the Oxford University Press.
As the fastest-growing group based on take-home pay, the new rich tend to enjoy better schools, employment and gated communities, making it easier to pass on their privilege to their children.
Their success has implications for politics and policy.
The group is more liberal than lower-income groups on issues such as abortion and gay marriage, according to an analysis of General Social Survey data by the AP-NORC Center for Public Affairs Research. But when it comes to money, their views aren't so open. They're wary of any government role in closing the income gap.
In Gallup polling in October, 60 percent of people making $90,000 or more said average Americans already had "plenty of opportunity" to get ahead. Among those making less than $48,000, the share was 48 percent.
"In this country, you don't get anywhere without working hard," said James Lott, 28, a pharmacist in Renton, Wash., who adds to his six-figure salary by day-trading stocks. The son of Nigerian immigrants, Lott says he was able to get ahead by earning an advanced pharmacy degree. He makes nearly $200,000 a year.
After growing up on food stamps, Lott now splurges occasionally on nicer restaurants, Hugo Boss shoes, and extended vacations to New Orleans, Atlanta, and parts of Latin America. He believes government should play a role in helping the disadvantaged. But he says the poor should be encouraged to support themselves, explaining that his single mother rose out of hardship by starting a day-care business in their home.
"I definitely don't see myself as rich," says Lott, who is saving to purchase a downtown luxury condominium. That will be the case, he says, "the day I don't have to go to work every single day."
Sometimes referred to by marketers as the "mass affluent," the new rich make up roughly 25 million U.S. households and account for nearly 40 percent of total U.S. consumer spending.
While paychecks shrank for most Americans after the 2007-2009 recession, theirs held steady or edged higher. In 2012, the top 20 percent of U.S. households took home a record 51 percent of the nation's income. The median income of this group is more than $150,000.
Once concentrated in the old-money enclaves of the Northeast, the new rich are now spread across the U.S., mostly in bigger cities and their suburbs. They include Washington, D.C.; Boston, Los Angeles, New York, San Francisco, and Seattle. By race, whites are three times more likely to reach affluence than nonwhites.
Paul F. Nunes, managing director at Accenture's Institute for High Performance and Research, calls this group "the new power brokers of consumption." Because they spend just 60 percent of their before-tax income, often setting the rest aside for retirement or investing, he says their capacity to spend more will be important to a U.S. economic recovery.