Over all, more than 50 percent of federal benefits flow to the 13 percent of the population over 65. Some of these benefits come from Social Security, which many people pay for over the course of their working lives. But a large chunk comes through Medicare, and contrary to widespread perception, most Americans do not come close to paying for their own Medicare benefits through payroll taxes. Medicare, in addition to being the largest source of the country’s projected budget deficits, is a transfer program from young to old.

Meanwhile, education spending — the area that the young say should be cut the least, polls show — is taking deep cuts. The young also want the government to take action to slow global warming; Congress shows no signs of doing so. Even on same-sex marriage, where public opinion is moving toward youthful opinion, all 31 states that have held referendums on the matter have voted against same-sex marriage.

Over the long term, obviously, the young have a distinct advantage: they’re not going away. So one of the central questions for the future of American politics is whether today’s 20- and 30-year-olds will hold on to many of the opinions they have today, a pattern that would be less surprising than glib clichés about aging and conservatism suggest. Until recently, as the presidential results from the 1970s through the 1990s make clear, Americans did not grow much more conservative as they aged.

And while today’s young are not down-the-line liberal — they favor private accounts for Social Security and have reservations about government actions to protect online privacy — they certainly lean left.

No one knows exactly why, but there are some suspects. Having grown up surrounded by diversity, they are socially liberal, almost unconsciously so. Many of them also came of age in the (ultimately unpopular) George W. Bush presidency, or the (ultimately popular) Bill Clinton presidency, and pollsters at the Pew Research Center argue that the president during a generation’s formative years casts a long shadow, for better or worse. Hammered by the economic downturn, young voters say they want government to play a significant role in the economy.

These attitudes create a challenge for the Republican Party that is arguably as big as its better known struggles for the votes of Latinos. “We’ve got a generation of young people who are more socially liberal and more open to activist government,” says Andrew Kohut, president of the Pew center, which has done some of the most extensive generational polling. “They are quite distinct.”