But during the past 25 years, the city changed. Both Washington and his successor, Richard M. Daley, worked hard to bridge racial divisions. By Election Day 2008, the white ethnics who held the balance of power in Chicago and the country as a whole sounded less like Archie Bunker and more like Studs Terkel.

For all of their narcissism, these baby boomers proved good at one thing—raising children. Their offspring, on balance, turned out to be more politically practical and socially responsible. Just as Franklin D. Roosevelt triumphed by mastering radio, these 20-somethings helped build Obamaworld by exploiting the dominant new political tool of our time, the Web. The irony is that the dreams of liberal parents could only be achieved when they relinquished generational power. By the end, even Bill Clinton was ready to champion Obama as "the future."

History will record that, like FDR in 1932 and Ronald Reagan in 1980, Obama won because the economy was bad. But big victories don't guarantee successful presidencies. It wasn't until Roosevelt and Reagan dented the problems of their day—made real change a reality—that they transformed American politics.

And so it will be for Obama. For now it's enough that the retired cops and the one-time hippies, and the African-Americans and Hispanics whom the whites never used to talk to much, and all their children and grandchildren gathered together on the same side of the barriers in Grant Park, in a place where they all belonged, just as Obama had hoped. Once again, the whole world was watching, only this time with a glad heart.

© 2008