There is a Sanders phenomenon. It is real, and the factors that have prompted its emergence need to addressed and understood.

When this year’s presidential primary began, many dismissed the Democratic Party contest as a “done deal”. It was assumed that Hillary Clinton would be the inevitable nominee — with the primaries and caucuses being a bothersome but required pro forma affair that Clinton would have to endure until she accumulates enough delegates to be declared the nominee.

One year ago, Clinton was leading the rest of the Democratic field by between 50 to 60 points, with none of her opponents believed to be serious challengers — especially not the 74-year-old socialist Senator from Vermont.

Back then, support for Bernie Sanders came largely from a core group of progressive activists who were driving his campaign. A year later, much has changed, with the gap between Clinton and Sanders, among Democrats, having narrowed to single digits.

When the preferences of all voters (Democrats, Republicans and Independents) are considered, and Clinton and Sanders are matched separately against the GOP’s nominee, Donald Trump, a very different picture emerges.

The average of this month’s polls shows Trump beating Clinton by slightly less than one point. The same polls averages show Sanders beating Trump by about 11 points. And polls in key battleground states show much the same: Clinton and Trump running neck and neck and Sanders beating Trump in every state.

That is what happened, but the question that needs to be answered is why.

Several factors point the way.

Part of Clinton’s problem is that she is running for president in a year when voter distrust of and even anger at the political and economic establishments has come to define the national mood.

Few voters believe that politicians and corporate leaders consider the public’s well-being in their decision making.

Given this setting, Clinton’s claim of experience and her long-standing ties to Wall Street investors have become liabilities.

In the contest between Clinton, the ultimate “insider”, and Sanders, the ultimate “outsider”, Sanders has a decided edge.

Then there are the matters of authenticity and trust.

Polls demonstrate that voters, especially the young and the growing number of those who declare no affiliation with either party, are drawn to Sanders because they see him as authentic and trust him.

Among voters under 45, Sanders beats Clinton by a margin of 2 to 1. And when all voters are asked who they trust more, Sanders wins by 3 to 1.

These two factors, distrust of the establishment and yearning for a leader who is authentic and can be trusted, form the underpinnings of the Sanders phenomenon. The “meat on the bones” is the issues he has championed.

America is, without a doubt, a wealthy nation. The gross domestic product and the performance of the stock market, despite an occasional dip, appear to suggest a healthy economy. But in spite of this, real incomes for the middle class have been stagnant for decades, leaving most Americans struggling to make ends meet.

When Sanders points out that the top 1 per cent in the US controls more of the nation’s wealth than the bottom 90 per cent, and when he notes that the American middle class controls a smaller percentage of our nation’s wealth than the middle class in any other industrialised countries, that message resonates.

As does his broader message of economic justice and a reordering of political/economic priorities.

While Sanders’ calls for “healthcare for all”, tuition-free higher education and to pay for these programmes by imposing stiffer taxes on the wealthiest 1 per cent are dismissed as unworkable and “socialist”, they have been embraced by young and working-class voters who are hungry for change.

And when he criticises the corrupting influence of “big money” in our politics, voters respond in agreement.

As this election is entering its final round, it is clear that the Sanders phenomenon must be taken seriously.

Despite the view of media pundits and the Democratic establishment that the contest is over (a form of voter suppression) and calls for Sanders to withdraw from the race, he continues to demonstrate electoral strength — winning two out of the last three and twelve out of the last twenty states.

At this point, Sanders can legitimately claim the support of about one-half of the Democratic Party’s base. This cannot be dismissed. Nor can his observation that he outperforms Clinton with independents and fares better against the GOP in national and battleground state polls.

Democrats would be making a mistake to ignore both the “meta issues” of distrust of the establishment and the voters’ desire to have a candidate they can trust, as well as Sanders’ far-reaching agenda for political and economic reform.

I believe that if he wins in California, Sanders can make a strong case urging the party’s super-delegates to support his candidacy.

It is this group — many of whom had endorsed Clinton before this election had even begun — that made her margin over Sanders appear to be insurmountable.

But even if he does not win, what he represents cannot be dismissed or reduced to any single issue, as many of the press reports on his platform picks attempted to do this past week.

What Sanders represents and the far-reaching change in domestic and foreign policy he has advocated and that many voters have endorsed should not be ignored.

Responding to voters’ deeply felt needs, Sanders has given birth to a true progressive movement that, if understood, embraced and, most importantly, sustained, can, as he has noted, bring revolutionary change to America.

It is a phenomenon.