Intervention is the central question of American foreign policy. When, where, and how should the United States project power abroad? Our answers help shape the world.

Debate over intervention has naturally become part of this season’s presidential campaign. Most candidates sing from the same foreign policy hymnal. They share deeply ingrained assumptions: The United States is the indispensable nation that must lead the world; this leadership requires toughness; and toughness is best demonstrated by the threat or use of force. It is the Cold War consensus, untouched by the 21st century.

Only one of the remaining candidates has broken from this orthodoxy. Bernie Sanders is often described as inexperienced in world affairs. Certainly he has spent far fewer hours thinking about global issues than his Democratic rival, Hillary Clinton. Yet recently he has found a theme: the long-term effects of intervention. Rather than cheer every show of American force, Sanders reminds us of the parlous consequences of past assaults on other countries.

This is a sharp break from our foreign policy catechism. Yet it is hardly new. Ever since the United States began intervening abroad more than a century ago, loud voices have been raised in dissent. Today’s protesters against foreign intervention are not a marginal fringe — “wacko birds,” as John McCain famously called them. They are deeply rooted in American politics. Unfortunately for Sanders, history shows that in the end, voters usually reject them.

Sanders does not simply censure American intervention as a vague or abstract concept. He has singled out several of the most misbegotten CIA operations, including the 1953 coup against Prime Minister Mohammad Mossadegh in Iran, the next year’s overthrow of President Jacobo Arbenz in Guatemala, the 1961 Bay of Pigs invasion of Cuba, and the Contra war in Nicaragua during the 1980s. Moving to more recent history, he has criticized Clinton for promoting intervention against the Libyan dictator Moammar Khadaffy in 2011 — a project that now seems disastrously misconceived.

Clinton proudly claims her place in the interventionist mainstream. So do all the Republican presidential candidates — including Donald Trump, who despite some unorthodox views remains an unapologetic champion of raw power. Only Sanders is truly skeptical of what American intervention can accomplish. He has shown himself to be just as far outside the Washington consensus on foreign policy as he is on domestic policy.

By rejecting the interventionist paradigm, Sanders places himself in a rich American tradition. It dates back to the movement against US annexation of the Philippines in 1898-99. “You have no right at the cannon’s mouth to impose on an unwilling people your Declaration of Independence and your Constitution and your notions of freedom and notions of what is good!” thundered Senator George Frisbie Hoar of Massachusetts. Mark Twain lamented that American leaders had “invited our clean young men to shoulder a discredited musket and do bandit’s work.”

These anti-imperialists, as they were then called, lost their battle by excruciatingly narrow margins. In the Senate, the treaty by which the United States annexed the Philippines and other island territories was ratified with one vote more than the required two-thirds margin. The Supreme Court upheld it in a 5-to-4 decision. Yet close as it was, victory for the interventionists was clear.

The tide of American intervention reached a peak with Woodrow Wilson, who promised to stop invading Latin America when its people learned “to elect good men.” It receded under the conservative Republicans who followed him. President Herbert Hoover, who had lived and worked in a dozen countries, gave Americans the unwelcome news that in “a large part of the world,” people saw the United States as “a new imperial power intent upon dominating the destinies and freedoms of other people.”

After World War II, most Americans embraced the Cold War narrative, but rebels arose from both ends of the political spectrum. Henry Wallace, a liberal Democrat, and Robert Taft, a conservative Republican, ran for president on platforms urging a more modest foreign policy — what some called “isolationism.” Both were trounced by candidates from the interventionist mainstream.

That same mainstream punished Senator George McGovern for his audacious break from political orthodoxy during the 1972 presidential campaign. McGovern lost 49 states after pledging, “Never again will we send the precious young blood of this country to die trying to prop up a corrupt military dictatorship abroad.” Other heretics, notably Pat Buchanan and Ron Paul, also failed to persuade voters that American interventions often do more harm than good.

Sanders is this generation’s embodiment of rebellion against foreign policy dogma. He sees much of America’s trouble in the world as the result our own shortsighted interventions. It is a trenchant insight. History suggests, however, that it makes bad politics.

Americans are inclined to action, not reflection. We favor leaders who promise total victory, not those who urge restraint and warn of long-term dangers. We cling to the belief that the United States should, can, and must guide the world. Candidates who tell us otherwise rarely thrive.

Stephen Kinzer is a senior fellow at the Watson Institute for International and Public Affairs at Brown University. Follow him on Twitter @stephenkinzer.