The political earthquake now shaking the pillars of the Republican Party throws into stark relief what is unique about campaign 2016 — that the fault line is not the typical polar clash of left vs. right, but a far more fundamental up-down cleavage between rank-and-file Americans and the power elite.

In both major parties, the primary campaign has unearthed a mass mutiny against the powers that be, reflecting a profound rift in American society with ramifications far beyond this year’s election.

For a moment, think of this year’s campaign as an MRI on America. Bernie Sanders and Donald Trump are exposing what Arnold Toynbee, the great British historian, called “schisms in the soul” of society.

House Speaker Paul Ryan and establishment Republicans like Mitt Romney, Jeb Bush and his family seek to cast the battle for the soul of the Republican Party as an urgent rescue of true conservativism, the ideology of the right. The Democratic establishment fears that Sanders will drag their party too far left. But at its core, the power struggle in both parties is over control, over who will determine America’s policy agenda — the party establishment or a disenchanted and now rebellious middle class.

The old paradigm of conservatives vs. liberals has been overturned by a rampant populism inherited from Occupy Wall Street and the populist roots of the tea party. In both parties, the central clash is Middle America vs. the power brokers, small donors vs. super PACs, the 99 percent vs. the 1 percent, agents of change vs. defenders of the status quo, shared prosperity vs. trickle-down economics, a neglected majority vs. an entrenched elite.

The gut issue is inequality — not just inequality of incomes but inequality of power, inequality of outcomes from America’s international trade agreements, inequality of who sets the nation’s policy agenda, inequalities of economic security and opportunity in an era of globalization, and inequalities of political voice and influence in an era of Citizens United and dark money.

True, since the Occupy movement put inequality on the map, it has been massively dissected. But for the first time, it now has real political consequences. We are a deeply divided country, perhaps less fundamentally by party ID than by money, power and certainly by whom we trust and distrust.

Trump, for example, could not have succeeded without the popular backlash against the GOP establishment, the loss of credibility among a string of veteran Republican governors and senators. Sanders would not still be winning primaries but for Hillary Clinton’s skidding favorability ratings because of mistrust about her elitism and her links to Wall Street.

Millions of Americans are disillusioned by what they see as a rigged political system, a popular suspicion documented by Princeton political scientist professor Martin Gilens and his colleagues in their multiyear study of 2,000 votes in the U.S. Senate. They proved what average Americans have long suspected: When it comes to making policy and passing laws, members of Congress are moved by the influence of the highly affluent and unmoved by majorities of middle class opinion.

To a degree unknown in decades, the corporate elite and billionaire mega-donors who are used to managing the selection of the GOP nominee to their own advantage, find themselves shut out, and their backlash is about trying to get back in control.

For it is not merely Trump’s barnyard rhetoric and racist, sexist bullying that causes tremors for Speaker Ryan and Republican thinkers and power brokers. What powerfully animates their anger is his rejection of pro-business Republican orthodoxy on free trade, immigration, social security and the minimum wage.

On the Democratic side, the party establishment and Clinton loyalists decry what they call the bogus lure of Sanders’ impractical idealism. But what many find so unnerving is the prairie fire of rebellion that Sanders has lit with his sallies against Wall Street, corporate trade deals, a lopsided tax system and politics dominated by mega-money.

Indeed, what has made Trump and Sanders so hard to deflate, defeat or derail is that both candidates, whatever their downsides, have given voice to what’s churning in the belly of America this year: A volcanic anger among middle-class Americans over being cut out of their fair share of America’s economic growth and being denied a serious voice in government.

Ten million-plus votes cast for Trump and 9 million-plus for Sanders reflect far more than opposition to other candidates. They represent populist antagonism to corporate America, and an erosion in public faith in American democracy and in the current version of American capitalism.

Time and again, pollsters report that 80 percent to 90 percent say our political system is broken, that corporations and special interests have too much power, and that Washington does not listen to average Americans. Most Americans voice a parallel loss of faith in the major institutions of our capitalist economy.

A Pew Research Center poll last November reported that 56 percent of the public said large corporations have a negative impact on the U.S. and only 41 percent of Republicans thought big business had a positive impact. Among 18-to-29-year-olds, a recent poll by Harvard’s Institute of Politics found that only 42 percent said they “supported” capitalism and just 19 percent identified themselves as “capitalists.”

In short, this campaign has identified the fault line in America today as wedge economics — the wedge between the nation’s economic growth and the middle class standard of living. That wedge emerged in the late 1970s and has widened ever since. Growth and productivity have risen dramatically over the past 30 years, but hourly wages of the average worker have been stagnant. Over that time, corporate profits have taken an ever larger share of the nation‘s income, and while the incomes of the 1 percent have soared, median household income is lower today than in 1999.

Not only economic progressives, but even some business leaders now see that this wide economic divide poses long-term peril for our country. Several years ago, before the economic collapse of 2008, the late John Gardner, the Republican founder of Common Cause, framed our predicament powerfully.

“We are treading the edge of a precipice here,” Gardner warned. “Civilizations die of disenchantment. If enough people doubt their society, the whole venture falls apart.”

An earthquake of disenchantment is now shaking the foundations of our political system — tremors that we need to heed.

By Hedrick Smith

Hedrick Smith is the author of “Who Stole the American Dream?” and the executive editor of the website reclaimtheamericandream.org. Readers may send him email at hsmithprod@gmail.com. He wrote this for the Sacramento Bee. — Ed.

(Tribune Content Agency/The Sacramento Bee)