The fault lines in the 2012 election are the future versus the past—and not in an empty rhetorical “America is at a crossroads” sort of way. Something more fundamental and demographically measurable is at work. Consider this:

President Obama’s largest margins of support come from voters under 30, women under 50, African-Americans, and Hispanics.

Mitt Romney’s largest margins of support come from senior citizens and white men.

The data are depressingly clear. According to the final Pew Poll, Obama is beating Romney by 28 points among voters under 30, while Romney is winning voters over age 65 by 10 points.

Romney is winning white men by a 21-point spread, with the president securing just 36 percent of their support. In turn, Obama is winning women under age 50 by a stunning 23 points.

And when diversity is taken into account, the gaps become even more stark. Romney is winning just 4 percent of black voters and only a quarter of Hispanics, on pace for the worst presidential performance with this fastest-growing demographic in America in modern political history.

In this sense, the 2012 election is the future versus the past, and it brings out barely slumbering tensions and resentments. Maybe that’s why the final CNN poll found that 37 percent of Romney supporters are primarily voting against Obama.

To some extent, these demographic divides are a reflection of the candidates themselves. Obama is 51 and not a white man. Romney is 65 and a very white man.

But the fault lines are embodied by the two parties themselves, characteristics evident in everything from the composition of Congress to the crowds at campaign rallies.

There are 40 black Democrats in the House of Representatives and two black Republicans. There are 17 Hispanic Democrats in the House and seven Hispanic Republicans. The GOP has made determined diversity gains in recent years—particularly when governors like Brian Sandoval, Susana Martinez, Nikki Haley, and Bobby Jindal are taken into account—but the gap remains wide.

A gender gap is evident in Congress as well. A quarter of House Democrats are women; while 10 percent of House Republicans are women.

The campaign rallies also reflect these divides. As Mark Halperin wrote recently: “Don’t kill me for the obvious, but the near absence of racial diversity in the Romney crowds is teased out further by the contrast with the rainbow the President draws. It is more striking than I have ever experienced it in any presidential campaign I have covered.”

The stark difference is largely unspoken because it is so obvious that it makes reporters and columnists, as well as supporters, uncomfortable discussing it. At Romney rallies, I’ve found myself playing “Where’s Waldo?” trying to find a person of color in the crowd. There are always a few, most often positioned on the bleachers behind the podium.

Before Democrats start feeling morally superior, the disparity is not evidence of racism. Instead, it reflects the differences between urban and rural communities in our country. It is a basic fault line of American politics, competing experiential bubbles that informed political differences going back to Jefferson and Hamilton’s debates, and divisions over Prohibition.

One more thing—the framing of this election as the future versus the past should not create a false sense of inevitability. The polls are tight, and there is no guarantee that the Democrats’ bet on the future will work this election. Team Obama has pursued a risky play-to-the-base campaign from the beginning, and as I’ve written, its strategy might be more suited to 2016 or 2020 than to 2012. Conservatives have done well, from Nixon 1968 on, in part as a check against tumultuous change. And that has been a quiet but core claim of the Romney campaign, with Paul Ryan telling a conference call of evangelical voters last night that Obama threatens “Judeo-Christian values,” as reported by Zeke Miller of BuzzFeed.

The demographic divisions are one reason why uniting the nation after the election will be difficult. If Obama loses a close reelection, he will remain a beloved pioneering political leader to a rising generation of Americans whom a President Romney will have a hard time inspiring. On the flip side, one of the open questions in this election is whether a reelected Obama will be granted the traditional degree of increased legitimacy in a second term by his opponents.

Republicans will need to reach out beyond their base to win elections in the future. Democrats are building their base on a segment of the electorate that is still ascendant. Here’s hoping that in future elections these demographic divides will diminish as we struggle in fits and starts to form a more perfect union.