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A man reads a newspaper with the headline that reads in Spanish: "Colombia said No" in Bogota, Colombia, Monday, Oct. 3, 2016. Voters rejected a peace deal with leftist rebels of the Revolutionary Armed Forces of Colombia, FARC, by a razor-thin margin in a national referendum Sunday, dismissing years of negotiations and delivering a setback to President Juan Manuel Santos.

(AP Photo/Fernando Vergara)

By Eugene Robinson

WASHINGTON -- I know, I know, the point I'm about to make is painfully obvious. But it is not in any sense trivial: If you care who wins the election next month, get off the couch, go down to your polling place and vote.

National polls taken since last week's debate show Hillary Clinton with a solid lead over Donald Trump; a Politico/Morning Consult poll released Monday morning, for example, put the gap at 6 points. New polls in swing states, including some that once looked favorable for Trump, also report that Clinton is now ahead. There is every reason to believe that most Americans favor the former U.S. senator and secretary of state over the bigoted, clownish real estate mogul who claims he's worth billions of dollars yet apparently avoids paying federal income taxes.

If you're tempted to think this is in the bag, however, look around.

In Colombia on Sunday, voters narrowly rejected a peace deal intended to end a war against leftist guerrillas that has raged for five decades and claimed tens of thousands of lives. Supporters of the agreement were shocked because respected polls had shown it would be approved easily.

Similarly, polls showed that British voters were in favor of remaining in the European Union. Yet when ballots were counted after the June 23 referendum, the "leave" position had won a slim victory. Many Britons were stunned and dismayed -- none more so than David Cameron, who was forced to resign as prime minister.

It is tempting to look at these results -- plus the election of dangerous lunatic Rodrigo Duterte as president of the Philippines -- and conclude that some sort of vast, perhaps unstoppable, anti-elite wave is sweeping the globe. As go Medellin and Manila, in other words, so goes Milwaukee.

I think there is a simpler, less apocalyptic explanation: In both Britain and Colombia, the outcomes were determined by those who didn't bother to vote.

For the Brexit referendum, overall turnout was high, a bit over 70 percent. But turnout among voters under 40 -- those most likely to favor remaining in the EU -- was only about 65 percent, according to a London School of Economics analysis. Meanwhile, turnout among those over 65, the group most likely to favor exiting the union, was an estimated 90 percent.

Had turnout among younger voters been a few points higher, Brexit would have lost.

In Colombia, a nation of 40 million people, the peace deal was rejected by just 54,000 votes. But turnout was a paltry 37 percent. If so many Colombians who favored the agreement hadn't assumed it was safe to stay home, believing the outcome was a foregone conclusion, President Juan Manuel Santos would be taking a victory lap instead of scrambling to come up with a Plan B.

The lesson for American voters seems clear. Yes, this is a year when anti-establishment protest is finding expression at the ballot box. The Duterte case is instructive: Filipino voters knew they were choosing as president a man who believes the way to deal with illegal drugs and rampant crime is through extrajudicial summary execution. They may come to regret their choice, but they made it with open eyes.

In Britain and Colombia, however, majorities of voters sabotaged themselves with their own apathy. And the only way Trump can win is if the same thing happens here.

It is true that the white working-class voters who form the core of Trump's support do not always show up on Election Day. But given their fervor for the bombastic GOP candidate -- who claims, ridiculously, that he can hold back the tides of globalism, demography and science -- it is reasonable to assume that Trump's people will indeed vote.

But they are outnumbered, however, by voters who recognize Trump for the ignorant and dangerous charlatan that he is. Pollsters try to account for any enthusiasm gap when they screen for "likely" voters. But really there should be no gap at all.

The coalition of women, young people, African-Americans, Hispanics and Asian-Americans that twice elected President Obama has even more reason to come out in force to elect Clinton. Anyone who believes that Trump is essentially harmless, or that he is so ridiculous a figure that inevitably he will lose, is whistling past the graveyard.

The Clinton campaign is setting in motion a get-out-the-vote campaign that represents the state of the art. Ultimately, however, this is on you. There is one sure way to avoid the nastiest of surprises on Nov. 8: Vote, or you'll have no right to complain.

Eugene Robinson's email address is eugenerobinson@washpost.com.

(c) 2016, Washington Post Writers Group