The day he lost the California primary Barack Obama said his campaign has unified Americans of all backgrounds in pursuit of a “common purpose.” Three weeks later, in Texas, he said the nation needs “leaders who can inspire the American people to rally behind a common purpose and a higher purpose.”

As long ago as 2000, Sen. John McCain similarly invited voters to “believe in a national purpose that is greater than our individual interests.” Winning the GOP nomination has hardly changed his mind on this point.

Obama and McCain appear to agree that Americans should have a common, national purpose. Notice the singular, indefinite article. Americans do not pursue a multitude of purposes but rather, one purpose.

The desire for a higher purpose is nothing new. Progressives have been demanding that American follow a national purpose for a century at least. The Progressive writer Herbert Croly (the founder of the New Republic) saw the American state as means of attaining a common, national purpose which he identified with “a morally and socially desirable distribution of wealth.” Obama and his supporters would no doubt agree.

Croly also had nothing but contempt for such self-interested activities as business and the pursuit of wealth. Individuals, he argued, should rise above mere commerce. Sen. McCain believes, as he put it during the GOP debate prior to the California primary, that “patriotism not profit” motivates a true leader.

Hence McCain believed that Mitt Romney, a mere businessman turned one-term governor, could never truly lead the nation.

To be sure, the two candidates would pursue different ideas about our common purpose. President Obama would seek to redistribute wealth to reduce inequality. The voters who receive this windfall would be satisfied and no doubt supportive of the policy and the new president. Some voters who would be taxed to provide the money for redistribution would also be satisfied.

But others who pay the taxes to support the redistribution would not be happy. They might deny that the nation has a common purpose to make wealth more equal. At that point, the nation would not have a common purpose but rather disagreement about what the government should do.

Sen. Obama believes such disagreements can be overcome by leaders who inspire citizens to transcend their disagreements. That transformation is unlikely. The economist Alberto Alesina has found that Americans are not bothered much by inequality compared to Europeans.

Sen. McCain has emphasized the importance of winning the war against terrorism. It is true that threats to national survival unite a nation. After Pearl Harbor, the nation worked largely as one to defeat the Axis powers. The same could be said prior to 1968 about the Cold War in general; almost all Americans supported efforts to stop the spread of Communism.

But Iraq is not a war of national survival. According to President Bush, it is a war to improve the lives of a foreign people by bringing them the benefits of democracy. Sen. McCain has stalwartly defended the effort in Iraq; he may well see a crusade to improve other lands as a national purpose that should trump individual interests.

Many, sometimes most, Americans do not agree. Polls that ask whether the war has been worth the cost have garnered deeply divided responses from the public. The war divided the nation rather than united citizens behind a common purpose.

The problem here is not just that Americans do not like this war or that idea of equality. The problem is that both Obama and McCain misunderstand the American political tradition.

Americans are not soldiers in an army seeking victory in war, or employees of a business seeking to maximize its profits. They are not members of a church defined by their common effort to save sinners or aid the poor. The United States is not an organization pursuing a single, common purpose.

It is rather a government instituted by individuals to protect their rights to life, liberty, and the pursuit of happiness. In exercising those rights, individuals will pursue many purposes and many ways of living. This ideal of individual liberty and limited government has little in common with Progressive crusades to enforce an equality of condition or to create democracies in far off lands.

Neither Thomas Jefferson nor Ronald Reagan will be on the presidential ballot this year. Two Progressives rather like Theodore and Franklin Roosevelt will be there, talking about big sticks, crusades, and “reform.”

Once in office, however, the new president will have to enlist ordinary Americans in pursuit of a common, national purpose. At that moment, the new president will discover that American individualism was not dead but merely sleeping in 2008.