To grasp how powerfully demographic change is reshaping the political landscape try this thought experiment about the 2008 election.
Start by considering the electorate's six broadest demographic groups -- white voters with at least a four-year college degree; white voters without a college degree; African-Americans; Hispanics; Asians; and other minorities.
Now posit that each of those groups voted for Barack Obama or John McCain in exactly the same proportions as it actually did. Then imagine that each group represented the share of the electorate that it did in 1992. If each of these groups voted as it did in 2008 but constituted the same share of the electorate as in 1992, McCain would have won. Comfortably.
That's because Obama's best groups are much larger today than in 1992. From 1992 to 2008, the share of the vote cast by African-Americans jumped from 8 percent to 13 percent. For Hispanics the share soared from 2 percent to 9 percent; for Asians and other minorities combined, from 2 percent to 5 percent. Meanwhile, the percentage of the vote cast by well-educated whites remained unchanged at 35 percent. The big losers were blue-collar whites -- those without college degrees -- whose share plummeted from 53 percent in 1992 to just 39 percent now.
That's a threat to the GOP because those culturally conservative, working-class whites are today its most reliable voters. McCain won 58 percent of them, and Obama just 40 percent. Obama, by contrast, won 95 percent of African-Americans, 67 percent of Hispanics, 66 percent of other minorities, 62 percent of Asians, and 47 percent of college-educated whites. Apply those results to the 1992 share of the vote for all six groups, and McCain beats Obama, 50.2 percent to 47.9 percent.
It's reasonable to assume that whenever Obama ran, he would have boosted black turnout. From 2004 to 2008, the share of the vote cast by African-Americans increased by nearly one-fifth. If you increase the share of the vote cast by blacks in 1992 by that amount -- and offset their gains with equal reductions among college and noncollege whites -- the result tightens, but McCain still edges out Obama, 49.2 percent to 49.1 percent. The distance between these "fantasy baseball" results and Obama's 7-point real-world victory underscores the political impact of demographic change. The problem for Republicans is that the population trends boosting the Democrats show no sign of slowing.
Today non-Hispanic whites make up two-thirds of the U.S. population. But in 2008 they still cast 74 percent of the ballots in the presidential contest. African-Americans represent about the same share of the vote (13 percent) as they do of the population (12 percent). So do "other" minorities (3 percent and 2 percent).
Asians, meanwhile, are modestly underrepresented in the electorate (2 percent of voters; 4 percent of population). And Hispanics are severely underrepresented (just 9 percent of voters compared with 15 percent of population).
The Census Bureau projects that the white share of the overall population will decline to 60 percent by 2020 and 51 percent by 2040. The black population share will remain largely unchanged; Asian and "other minority" shares of the population will grow steadily (to nearly 11 percent combined by 2040); and the Hispanic presence will explode. By 2020, Hispanics are projected to constitute nearly one-fifth of the population; by 2040, more than one-fourth.
William Frey, a prominent Brookings Institution demographer, says that even as those numbers rise, the gap will steadily narrow between Hispanic representation in the population and in the electorate. "The biggest source of Hispanic population growth is not immigration, but from the children of recent immigrants. And, by definition, they are voting citizens once they turn 18," he says. Whites may still outvote their population numbers, Frey predicts, but as Hispanic participation increases, the white overrepresentation will diminish. That change promises an increasingly nonwhite electorate.
These trends point toward trouble for the GOP if it cannot attract more minorities, especially Hispanics, and reverse the recent Democratic inroads among well-educated whites.
The best way to illustrate that prospect is to pitch the thought experiment forward 12 years. Imagine that the major demographic groups voted as they did in 2008, but cast a share of the vote equal to their expected share of the population in 2020. (For argument's sake, let's divide whites among college and noncollege voters in the same proportions as today.) In that scenario, Obama beats McCain by nearly 14 points -- almost twice as much as in 2008. Demography will indeed be destiny if Republicans can't broaden their reach.