The vitriol is worse than I ever recall. Worse than the Palin-induced smarm of 2008. Worse than the swift-boat lies of 2004. Worse, even, than the anything-goes craziness of 2000 and its ensuing bitterness.

It’s almost a civil war. I know families in which close relatives are no longer speaking. A dating service says Democrats won’t even consider going out with Republicans, and vice versa. My email and Twitter feeds contain messages from strangers I wouldn’t share with my granddaughter.

What’s going on? Yes, we’re divided over issues like the size of government and whether women should have control over their bodies. But these aren’t exactly new debates. We’ve been disagreeing over the size and role of government since Thomas Jefferson squared off with Alexander Hamilton, and over abortion rights since before Roe v. Wade almost 40 years ago.

And we’ve had bigger disagreements in the past ― over the Vietnam War, civil rights, communist witch hunts ― that didn’t rip us apart like this.

Maybe it’s that we’re more separated now, geographically and online.

The town where I grew up in the 1950s was a GOP stronghold, but Henry Wallace, FDR’s left-wing vice president, had retired there quite happily. Our political disagreements then and there didn’t get in the way of our friendships. Or even our families ― my father voted Republican and my mother was a Democrat. And we all watched Edward R. Murrow deliver the news, and then, later, Walter Cronkite. Both men were the ultimate arbiters of truth.

But now most of us exist in our own political bubbles, left and right. I live in Berkeley, Calif., a blue city in a blue state, and rarely stumble across anyone who isn’t a liberal Democrat. (The biggest battles here are between the moderate left and the far left.) TV has hundreds of channels, so I can pick what I want to watch and who I want to hear. And everything I read online confirms everything I believe, thanks in part to Google’s convenient algorithms.

So when Americans get upset about politics these days, we tend to stew in our own juices, without benefit of anyone we know well and with whom we disagree ― and this makes it almost impossible for us to understand the other side.

That geographic split also means more Americans are represented in Congress by people whose political competition comes from primary challengers ― right-wing Republicans in red states and districts, left-wing Democrats in blue states and districts. And this drives those who represent us even further apart.

But I think the degree of venom we’re experiencing has deeper roots.

The nation is becoming browner and blacker. Most children born in California are minorities. In a few years, America as a whole will be a majority of minorities. Meanwhile, women have been gaining economic power. Their median wage hasn’t yet caught up with men, but it’s getting close. And with more women getting college degrees than men, their pay will surely exceed male pay in a few years. At the same time, men without college degrees continue to lose economic ground. Adjusted for inflation, their median wage is lower than it was three decades ago.

In other words, white working-class men have been on the losing end of a huge demographic and economic shift. That’s made them a tinderbox of frustration and anger, eagerly ignited by Fox News, Rush Limbaugh and other peddlers of petulance, including an increasing number of Republicans who have gained political power by fanning the flames.

That hate-mongering and attendant scapegoating ― of immigrants, blacks, gays, women seeking abortions, our government itself ― has legitimized some vitriol and scapegoating on the left as well. I detest what the Koch Brothers, Karl Rove, Grover Norquist, Rupert Murdoch and Paul Ryan are doing, and I hate their politics. But in this heated environment, I sometimes have to remind myself I don’t hate them personally.

This degree of divisiveness would not have taken root had America preserved the social solidarity we had two generations ago. The Great Depression and World War II reminded us we were all in it together. We had to depend on each other in order to survive. That sense of mutual dependence transcended our disagreements. My father, a “Rockefeller Republican,” strongly supported civil rights and voting rights, Medicare and Medicaid. I remember him saying, “We’re all Americans, aren’t we?”

To be sure, we endured 9/11, we’ve gone to war in Iraq and Afghanistan, and we suffered the Great Recession. But these did not bind us as we were bound together in the Great Depression and World War II. The horror of 9/11 did not touch all of us, and the only sacrifice George W. Bush asked of us was that we kept shopping. Today’s wars are fought by hired guns ― young people who are paid to do the work most of the rest of us don’t want our own children to do. And the Great Recession split us rather than connected us; the rich grew richer, the rest of us grew poorer and less secure.

So we finish a bitter election feeling as if we’re two nations rather than one. The challenge, not only for our president and representatives in Washington but for all of us, is to rediscover the public good.

By Robert B. Reich

Robert B. Reich, chancellor’s professor of public policy at the University of California and former U.S. secretary of labor, is the author of “Beyond Outrage: What has gone wrong with our economy and our democracy, and how to fix it,” a Knopf release now out in paperback. ― Ed.