Many are working overtime to convince us that fringe candidates are serious — none more so than Sen. Bernie Sanders, Hillary Clinton’s only official opponent (so far) for the Democratic nomination for president in 2016.

Don’t believe it. Sanders is running on one of the most discredited ideas in history, the idea that socialism can work better than free markets and individual choice.

That’s Bill Press’ take in The Hill newspaper.

“Last Thursday … Vermont Sen. Bernie Sanders, a self-described ‘Democratic socialist,’ jumped into the race,” Press wrote. “Granted, with no national organization and no super-PAC, his candidacy is a long shot at best. Win or lose, he will have a profound, positive impact on the Democratic race for president in 2016.”

Press’ fondness for Sanders shines through.

“For progressives, Sanders’ presence is especially important because he will champion and force debate on issues Clinton might not have otherwise talked about. Sanders believes campaigns should mean ‘serious debates about serious issues,’ and that’s what he’ll deliver,” he pledges. “Where she often hesitates to take a stand, he never does. On any issue.”

Of course, there’s already a big push in the Democratic Party to drop the label of “socialist” (though it’s how Sanders describes himself).

“Stop Calling Bernie Sanders a socialist,” the New Republic demanded last week. “The Vermont senator is a ‘democratic socialist’ — and yes, there’s a difference.”

The magazine continued, “America is partly a social democracy already, of course, thanks to programs such as Social Security, Medicare and Medicaid, unemployment insurance, and food stamps. Sanders doesn’t want the government to run the entire economy, but he does want the government to ensure that the economy doesn’t regularly ruin millions of people’s lives.”

Why is the New Republic so adamant? Because there are few ideas in history as thoroughly discredited as socialism.

Now, socialism is a fine idea — in theory. Some of the best-intentioned people in history have tried it, including the early Christian Church and even the Pilgrims in the Mayflower colony.

But everywhere, and every time, it collapsed under the weight of human nature.

How wonderful this world would be if each person contributed what he could and took only what he needed.

But we don’t live in that world. We live in the real world, in which people want to be rewarded for their work — or else they won’t do it. Socialism denies one fundamental flaw in human nature that people are, for lack of a better term, selfish. If their reward is guaranteed, they’ll only work as hard as they have to. Plus, they’re greedy. They’ll take whatever they can.

People also are fallible.

Like socialism, planned economies always fail because of planners. The result always is disappointing, so much so that every socialist government has had to result to shooting or jailing its opposition.

That’s happening today in Venezuela, a lush tropical nation with rich oil reserves, which cannot even feed itself — because of socialism. Dissenters are rounded up and imprisoned.

Sanders isn’t a serious candidate because he brings no serious ideas to the table.