During the 2008 primaries, Hillary Clinton criticized Barack Obama after he cited Ronald Reagan’s presidency as an example of the impact he hoped to achieve. Reagan “changed the trajectory of America,” Obama told a Nevada newspaper, adding, “He put us on a fundamentally different path because the country was ready for it.” Obama’s point was not that he admired Reagan’s policies but rather that, like Reagan, he wanted to redefine what is viewed as possible in our politics.

Eight years later, with primary season officially in full swing after Monday’s Iowa caucuses, another insurgent candidate has upended the Democratic nomination contest by promising to take the nation down a different path. Campaigning on bold, progressive ideas such as free college tuition and Medicare for all, Sen. Bernie Sanders (I-Vt.) has prompted a backlash from not only Hillary Clinton and her supporters but also a posse of centrist and liberal pundits who have charged that such ideas are left-wing fantasies — popular, yes, but also politically impossible. In the past week alone, for example, The Post’s editorial board published two negative commentaries on Sanders, arguing that his campaign is premised on “fantastical claims” and “overpromising.”

Even more problematic to some critics is how Sanders vows to pay for his plans: by increasing taxes, even on the middle class. Despite professing his adoration for Sanders, Post columnist Dana Milbank recently declared, “Democrats would be insane to nominate him,” in part because he has “admitted he would seek massive tax increases.” He went on to ask: “Are Democrats ready to accept ownership of socialism, massive tax increases and a dramatic expansion of government? If so, they will lose.” Leaving aside the question of Sanders’s “socialism,” the upshot of this argument is that openly calling for higher taxes, even to fund popular government benefits, is a surefire political loser.

But it’s long past time for Democrats to seriously challenge this assumption, which has prevailed ever since Reagan ushered in his vision more than three decades ago. Indeed, while Republican candidates incessantly compete for the Reagan mantle by promising to slash taxes and spending, too many Democrats have tacitly consented to the orthodoxies of the policy framework he created. Tax increases once were recognized as a responsible way to fund essential government services, such as rebuilding roads and bridges, protecting clean air and water, and providing for our veterans. Today, political elites’ general aversion to raising taxes makes it increasingly difficult for government to function and virtually guarantees its inability to pay for new programs that could benefit millions of people, especially the middle class.

Fortunately, some progressive lawmakers are trying to change this destructive dynamic. One idea with growing momentum is a financial transaction tax, or “Robin Hood tax.” By imposing a tiny fee on stock trades and other financial transactions, supporters argue the tax could raise hundreds of billions of dollars with the added benefit of discouraging reckless high-frequency trading on Wall Street. The idea boasts an impressive roster of supporters, including Bill Gates and former Reagan budget director David Stockman. In Congress, Rep. Keith Ellison (D-Minn.) has introduced a financial transaction tax bill in the House, attracting 35 Democratic co-sponsors, while Sanders and Sen. Brian Schatz (D-Hawaii) are sponsoring the Senate version. In the presidential race, Sanders has called for using the revenue from the tax to make college more affordable, providing a concrete example of what can be accomplished through smart tax increases. Meanwhile, Clinton has proposed a more limited tax on high-frequency trading.

Yet, while demanding that Wall Street and the wealthy pay their fair share is a good start (and good politics), it’s not enough on its own. To escape the cruel grip of austerity, we need to have an adult conversation about the tradeoffs between taxes and crucial public investments. Until that happens, the best we can hope for is a watered-down version of Reaganomics, which poses a serious problem for Democrats regardless of whether Clinton or Sanders is the nominee. As former labor secretary Robert Reich wrote last week, “these days, nothing of any significance is politically feasible and every bold idea is a recipe for gridlock. This election is about changing the parameters of what’s feasible and ending the choke hold of big money on our political system.” And the best way to change what’s politically feasible is by radically changing the debate.

In a recent interview about the 2016 election, Obama echoed his comments from 2008, saying, “Bernie has tapped into a running thread in Democratic politics that says: Why are we still constrained by the terms of the debate that were set by Ronald Reagan 30 years ago?” It’s a critical question — especially for the millions of Americans who stand to benefit from the new kind of politics at the heart of Sanders’s campaign.

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