During every presidential campaign, pontificators solemnly declare that this is the most important presidential election of our lifetimes — a turning point in American history. Every election does mark a turning point of a kind, though in normal times it lasts four to eight years, as we zigzag from the center-left to the center-right. I wonder, though, if this time, our republic is about to tip over into an era unlike any we've seen since the 1960s, and perhaps the 1850s. The political norms that have held our factionalized nation together are coming apart at the seams. No matter who wins next Tuesday, we seem to be hurtling toward a constitutional crisis.

The rift between red and blue America has opened to a chasm of mutual contempt and incomprehension. Politics has become overtly racialized, venomous, toxic — a civil war by other means. For the first time, a presidential nominee, Donald Trump, has declared before the election that the results will be "rigged" and invalid. If Trump ascends to the presidency, Ross Douthat predicts in The New York Times this week, there's a high likelihood of "major civil unrest," with Trump's caustic rhetoric serving to "pour gasoline" on protests and violence. He would take office burdened with multiple allegations that he's a sexual predator, and battling two lawsuits charging him with defrauding students of Trump University. If Hillary Clinton is elected, she will face congressional investigations of the Clinton Foundation and her email server even before she moves into the Oval Office. In some Republican circles, talk of impeachment has already begun. More openly, some Republicans are vowing to refuse to let her fill Supreme Court vacancies for her entire term — in effect, nullifying the presidential election. I have to believe our resilient nation will survive the coming crisis, as we have survived so many others. But Americans have reason to fear where we're headed.