This election is only tangentially a fight over policy. It is also a fight about meaning and identity - and that's one reason why voters are so polarized. It's about who we are and who we aspire to be.
President Obama enters the final days of the campaign with a substantial lead among women - about 15 points, according to the latest Washington Post/ABC News poll - and enormous leads among Latinos and African-Americans, the nation's two largest minority groups. Mitt Romney leads among white voters, with an incredible 2-1 advantage among white men.
It is too simplistic to conclude that demography equals destiny. Both men are being sincere when they vow to serve the interests of all Americans. But it would be disingenuous to pretend not to notice the obvious cleavage between those who have long held power in this society and those who are beginning to attain it.
When Republicans vow to "take back our country," they never say from whom. But we can guess.
Issues of race, power and privilege are less explicit this year than in 2008, but in some ways they are even stronger.
Four years ago, we asked ourselves whether the nation would ever elect a black president. The question was front and center. Every time we see the president and his family walk across the White House lawn to board Marine One, we're reminded of the answer.
The intensity of the opposition to Obama has less to do with who he is than with the changes in American society he not only represents but incarnates. Citing his race as a factor in the way some of his opponents have bitterly resisted his policies immediately draws an outraged cry: "You're saying that just because I oppose Obama, I'm a racist." No, I'm not saying that at all.
What I'm saying is that Obama's racial identity is a constant reminder of how much the nation has changed in a relatively short period of time. In my lifetime, we've experienced the civil rights movement, the countercultural explosion of the 1960s, the sexual revolution, the women's movement and an unprecedented wave of Latino immigration. Within a few decades, there will be no white majority in this country - no majority of any kind, in fact. We will be a nation of racial and ethnic minorities, and we will only prosper if everyone learns to give and take.
Our place in the world has changed as well. The United States remains the dominant economic and military power; our ideals remain a beacon for those around the globe still yearning to breathe free. But our capacity for unilateral action is diminished; we can assert but not dictate, and we must learn to persuade.
Obama's great sin, for some who oppose him, is to make it impossible to ignore these domestic and international megatrends. Take one look at Obama and the phenomenon of demographic change is inescapable. Observe his approach to international crises in places such as Libya or Syria and the reality of America's place in the world is unavoidable.
I'm deliberately leaving aside what should be the biggest factor in the election: Obama's policies. It happens that I have supported most of them, but of course there are legitimate reasons to favor Romney's proposals, insofar as we know what they really are - and the extent to which they really differ from Obama's.
In foreign affairs, judging by Monday's debate, the differences are too small to discern; Romney promises to speak in a louder voice and perhaps deploy more battleships, but that's about it.
Domestically, however, I see a clear choice. I consider the Affordable Care Act a great achievement, and Romney's promise to repeal it would alone be reason enough for me to oppose him. Add in the tax cuts for the wealthy, the plan to "voucherize" Medicare and the appointments Romney would likely make to the Supreme Court, and the implications of this election become even weightier.
Issues may explain our sharp political divisions, but they can't be the cause of our demographic polarization. White men need medical care, too. African-Americans and Latinos understand the need to get our fiscal house in order. The recession and the slow recovery have taken a toll across the board.
Some of Obama's opponents have tried to delegitimize his presidency because he doesn't embody the America they once knew. He embodies the America of now.
Eugene Robinson is a Pulitzer Prize winning columnist and writes for The Washington Post. He can be reached at firstname.lastname@example.org.