Jonathan Tasini ( @jonathantasini ) has been a frequent commentator on CNN and is a Bernie Sanders supporter. He challenged Hillary Clinton in the Democratic Senate primary in New York in 2006. He is the author of several books, president of the Economic Future Group and the publisher/editor of Working Life. The opinions expressed in this commentary are his own.

(CNN) Many observers may scratch their heads wondering how a crass billionaire can make inroads with working-class voters, but their confusion misses a critical point: The political revolt that benefited Donald Trump is not limited to the Republican Party, but is also in full fury inside the Democratic Party. Democrats, by embracing in the 1990s a series of bipartisan policies geared toward corporations at the expense of American jobs, have since failed to adequately defend America's working class, and those voters are making their presence felt at the ballot box as a result.

Recent polls show the frustrations they feel toward the Democrats pose a real danger in the race for the White House, depending on who ends up winning the nomination. Quinnipiac found a battle between Hillary Clinton and Donald Trump to be an essential tossup in three key swing states: Ohio Pennsylvania and Florida . Meanwhile, in West Virginia , 53% of Democratic voters said global trade deals take jobs away from American workers.

Establishment Democrats are trying to wave off a recurring theme in poll after poll, including the Quinnipiac numbers and Tuesday night's primary results: Bernie Sanders is a much stronger general election candidate versus Trump. A Reuters/Ipsos poll released Wednesday even showed Donald Trump and Hillary Clinton running nearly neck-and-neck nationally.

Leaving aside Florida (which has been closely contested in recent presidential elections), the three other states tell an important story. Since the mid-1990s, a broad swath of American workers has felt shut out of every debate over economic recession or recovery. Particularly for those workers who once had unionized, middle-class jobs with solid benefits, finding decent-paying jobs has been a bust. According to Public Citizen's analysis of official government statistics since 1994, both Ohio and Pennsylvania have lost over 300,000 good-paying manufacturing jobs each.

That same time period coincides with the passage and implementation of the North American Free Trade Agreement and the creation in 1995 of the World Trade Organization. Both were championed by Bill Clinton, and his Labor Secretary Robert Reich, and endorsed by both parties. These so-called "free trade" deals have one common thread: They set up rules benefiting corporate rights, particularly the protection of capital and patents, at the expense of wages for workers

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During the 1990s, President Clinton also urged many Democrats to support other corporate-friendly measures: deregulation of the financial industry (which arguably set the stage for the recent financial crisis), welfare reform (which ripped away a safety net for millions) and tax cuts for the wealthy that exacerbated the divide between rich and poor. Enjoy getting your high cable bills every month? You can thank the Clinton administration's 1996 deregulation of telecommunications, which ushered in a wave of anti-consumer mergers. Indeed, the much-ballyhooed Clinton economic "miracle" was significantly built on a credit bubble, not robust or sustainable wage growth.

Today's rejoinders to criticism of these policies from many establishment Democrats underscore how tone deaf the party elites have become. They claim that things would be a lot worse if Republicans had been running the show. Without a doubt, I believe that to some extent, that is true. However, "Hey, vote for us because we're not as bad as the other guys" is a lackluster slogan — a wheezing plea that lacks credibility for many voters who have been ignored for decades.

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Democrats' longtime backing for corporate-friendly policies has, unsurprisingly, created fertile ground for the appeal of a huckster who pledges to "make America great again." Many voters are flocking to Trump not based on a complete list of specific policies they dislike on the left or support on the right. They just see a tidal wave of mounting debt, no hopes for a good job and, by contrast, the game they're losing being rigged in favor of a tiny group of people.

Working-class voters have a sometimes inchoate sense the political establishment -- anyone with experience serving in public office — has abandoned them to suffer while aligning themselves with forces many people can describe only vaguely as "Washington." Trump, who is schooled in the ability to sell anything and has a finely attuned ear to people's wounds and desires, can promise in grand terms to heal their hurt — even if he has no intention of doing so.

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With Hillary Clinton's record-high negatives in the area of t rust and honesty — exceeded only, to her good luck, by Trump's even higher negatives on those attributes — she will struggle to convince these voters that she feels their pain. She'll gain some traction thanks to Trump's sexism and the Republicans' relentless assaults on her. But the fact remains that she, like her husband did, has advocated the bipartisan policies that have hurt working Americans and she represents the very establishment people are aching to kick to the curb.

By contrast, Sanders' authenticity and his consistent opposition to the policies people feel, in their gut, have hurt them continues to resonate. Indeed, in the wake of Sanders' victory in West Virginia, even New Hampshire state Sen. Lou D'Allesandro, a Clinton supporter, told the Wall Street Journal : "Every time [Mr. Sanders] presents himself and presents his story, more people start talking about him."

People talk — and voters turn out — because Bernie Sanders' story is powerful. It describes, truthfully, what has happened to the working class in America. As a result, he is winning the debate about what the party should stand for — forcing a moderate, corporate-funded Democrat like Hillary Clinton to mimic his rhetoric and agenda. As we move into the final phase of primary season, we will soon know whether the party will also field the stronger opponent to the snake oil Donald Trump is selling.