WASHINGTON — It’s not just the wealthiest 1 percent.

Fully 20 percent of U.S. adults become rich for parts of their lives, wielding outsize influence on America’s economy and politics. This little-known group may pose the biggest barrier to reducing the nation’s income inequality.

The growing numbers of the U.S. poor have been well documented, but survey data provided to The Associated Press detail the flip side of the record income gap — the rise of the “new rich.”

Made up largely of older professionals, working married couples and more educated singles, the new rich are those with household income of $250,000 or more at some point during their working lives. That puts them, if sometimes temporarily, in the top 2 percent of earners.

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.

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.