The demographic wave reshaping the nation, like most changes in American life, is cresting among the young.

The first cache of results from the 2010 census found that minorities now comprise almost 37 percent of the nation's overall population. But that figure rises to nearly 47 percent among Americans younger than 18. Hispanics alone now account for nearly one-fourth of the kids in America.

This change isn't confined to a few big cities that have long attracted immigrants. Between 2000 and 2010, the minority share of the youth population increased in all 50 states. Brookings Institution demographer William Frey projects that minorities will constitute an absolute majority of children by the end of this decade.

The rise of this diverse youth population is one of the two most important demographic trends reconfiguring our economy, society, and politics. The second mirrors the first: As the baby boomers move into retirement, the number of seniors is steadily increasing. The trustees of Social Security and Medicare recently projected that those two giant programs for the elderly will be serving 80 million people in 2030, up from 40 million today.

However, those seniors present a different face than the emerging youth population does. Because the United States sharply limited immigration from 1924 until 1965, fully four-fifths of today's seniors are white. Demographers like Frey don't expect that proportion to change much for decades.

Of all the political challenges that the U.S. faces in the coming years, none may be more pressing, or perplexing, than reconciling the diverging interests of these two giant generations — the brown and the gray.

In the brown community, the dominant view is that government investments in education, health care, and social-welfare programs are indispensable if the growing number of minority children are to ascend to the middle class. But the graying white population has grown increasingly skeptical of government involvement and resistant to paying the taxes needed to fund the public investments that most of those minority families favor.

Neither the gray nor the brown is a monolith. Polls suggest that support for activist government isn't quite as widespread among Hispanics or Asian-Americans as it is among African-Americans; and even seniors who march in tricornered hats at tea party rallies are often fierce in their defense of Medicare and Social Security. But on almost any poll question that tests attitudes toward government's role in society, minority groups tilt toward support for activism while older whites increasingly oppose it.

The irony is that the gray need the brown more than they realize.

The two groups diverge as starkly in their voting behavior. In the 2008 presidential election, President Obama won the support of two-thirds of those under 30 and four-fifths of minority voters. Almost three-fifths of white seniors, meanwhile, preferred John McCain. In the GOP's 2010 congressional rout, the Republican tally among white seniors swelled to 63 percent — one of the party's best showings ever — while 73 percent of voters from racial and ethnic minorities stuck with the Democrats.

I don't believe those contrasting preferences are explained mostly by racial prejudices; rather, the evidence suggests they are driven more by historical allegiances, attitudes toward government, and perceptions about the parties' stances on civil rights and related issues, such as immigration.

But whatever the causes, the effect is clear. American politics today presents an escalating clash between a Republican Party that receives about 90 percent of its votes from whites and is committed to retrenching government and a Democratic Party that relies heavily on minority votes and is committed to defending an activist government role. Unless we reach a new social consensus, those warring perspectives threaten decades of political polarization with an ominous racial and ethnic edge.

The irony is that the gray need the brown more than they realize. The minority kids filling the United States' classrooms are the country's next workforce. Unless the nation does a better job of providing them a quality education, they're unlikely to find well-paying jobs — or to generate the payroll taxes needed to fund Social Security and Medicare. As usual, our fates as Americans are more intertwined than we recognize. If we don't create more economic opportunity for the brown, we'll never ensure financial security for the gray.


The author is the editorial director of National Journal.