Some elections are defined by the gap between the rich and the poor. Others are defined by the gap between the left and the right. But this election will be shaped by the gap within individual voters themselves — the gap between their private optimism and their public gloom.

American voters are generally happy with their own lives. Eighty-six percent of Americans say they are content with their jobs, according to the General Social Survey. Seventy-six percent of Americans say they are satisfied with their family income, according to a Pew Research Center survey. Sixty-two percent of Americans expect their personal situation to get better over the next five years, according to a Harris Poll, compared with only 7 percent who expect it to get worse.

 Researchers from Pew found that 65 percent of Americans are satisfied overall with their own lives — one of the highest rates of personal satisfaction in the world today.

On the other hand, Americans are overwhelmingly pessimistic about their public institutions. That same Pew survey found that only 25 percent of Americans are satisfied with the state of their nation. That 40-point gap between private and public happiness is the fourth-largest gap in the world — behind only Israel, Mexico and Brazil.

Americans are disillusioned with the president and Congress. Eighty percent of Americans think this Congress has accomplished nothing.

Sixty-eight percent of Americans think the country is on the wrong track. Sixty-two percent think that when government runs something, it is usually inefficient and wasteful. Sixty percent think the next generation will be worse off than the current one. Americans today are more pessimistic about government's ability to solve problems than they were in 1974 at the height of Watergate and the end of the Vietnam War.

This happiness gap between the private and the public creates a treacherous political vortex. On the one hand, it means voters are desperate for change. On the other hand, they don't want a change that will upset the lives they have built for themselves.

On the one hand, they want the country's political leaders to take bold action. On the other hand, they are extremely cynical about those leaders and are unwilling to trust them with anything that seems risky.

More than that, the happiness gap provides a lesson in what people want from their government in 2007. The polling — and I, for one, believe people are pretty sensible when it comes to evaluating their own lives — suggests that people are not personally miserable or downtrodden.

Their homes are bigger. They own more cars. They feel more affluent. In a segmented nation, they have built lifestyle niches for themselves where they feel optimistic and fulfilled.

But they also feel that their neighborhood happiness is threatened by global problems that are beyond their power to control: terrorism, rising health care costs, looming public debt, illegal immigration, global warming and the rise of China and India. They regard these looming problems the way people used to think about crime — as alien intrusions into their private tranquillity. And government seems to be doing nothing about them.

These voters don't believe government can lift their standard of living or lead a moral revival. They want a federal government that will focus on a few macro threats — terrorism, health care costs, energy, entitlement debt and immigration — and stay out of the intimate realms of life. They want a night watchman government that patrols the neighborhood without entering their homes.

This is not liberalism, which inserts itself into the crannies of life. It's not conservatism, suspicious of federal power. It's a gimlet-eyed federalism — strong government with sharply defined tasks.

If one were to advise a candidate about the happiness gap, you'd say: first, don't try to be inspiring or rely on the pure power of authenticity. In these cynical days, voters are not interested in uplift.

Second, don't propose any program that will interfere with the way voters are currently organizing their lives. They don't want you there.

Third, don't expect people to cast votes according to their income. Democrats do as well among top earners as Republicans. People are more interested in repairing the nation's health than in boosting their personal bottom line.

Fourth, offer voters a few big proposals (and strategies to implement them) that respond to global threats. Repeat those proposals at every event and forget about everything else.

In 1933, Franklin Roosevelt could launch the New Deal because voters wanted to change the country and their own lives. But today, people want the government to change so their own lives can stay the same. Voters don't want to be transformed; they want to be defended.