The United States faced fundamental decisions about foreign policy after World War II. Germany and Japan had been defeated, but the Soviet Union had emerged as a new threat. Mao Zedong’s forces were on the move in China. Would we engage or step away?

That was the situation when Sen. Arthur Vandenberg coined one of the most enduring aphorisms in American foreign affairs: “Politics stops at the water’s edge.”

Vandenberg, a Michigan Republican who chaired the Senate Foreign Affairs Committee, worked with the administration of Democratic President Harry Truman to forge a bipartisan consensus that included support for the Marshall Plan, NATO, and the Truman Doctrine, which held that the U.S. would intervene when its allies were threatened. Those actions helped keep us safe and secure for generations.

Today, the idea that foreign policy might be off limits to politics can seem unrealistic, even quaint. Partisanship seems to pervade our lives, from the media we consume to the cars we drive to the food we eat.

Vandenberg’s aphorism both reflected and shaped reality for years. During the Cold War, both parties were reliably anticommunist and opposed to Soviet aggression, although Republicans may have been more hawkish in their rhetoric. Both parties favored alliances and engagement with our allies. Over time, the idea that politics should stop at the water’s edge developed a secondary meaning: that politicians shouldn’t air their partisan disputes when traveling overseas. The idea was that presenting a united front to our allies and adversaries would make America stronger.

We often think of the Vietnam War as dividing the country, but those divisions weren’t strictly partisan. The 1964 Gulf of Tonkin Resolution, authorizing escalation of the war, passed unanimously in the House and with only two negative votes in the Senate. In the 1968 presidential election, voters saw little difference between Republican Richard Nixon and Democrat Hubert Humphrey in how they would handle Vietnam.

Americans usually unite in times of crisis and war. After 9/11, only one member of Congress voted against authorizing the use of force against those who were responsible. Early support for the wars in Afghanistan and Iraq was bipartisan, although support from both parties cooled as the wars dragged on.

Of course, political parties have always differed on how to conduct foreign policy. At the country’s founding, the Federalists favored international trade while the Jeffersonians focused on internal affairs. Even in 1948, when Vandenberg was working with Truman, some Republicans were accusing the president of being soft on communism.

Today, the foreign policy divides seem substantially wider. A key example is Ukraine, where Democrats are far more likely than Republicans to support military aid. Congressional Republicans aligned with former President Donald Trump blocked $60 billion for Ukraine for months before it was finally approved in April.

Other international issues also expose partisan fault lines. According to surveys by the Pew Research Center, most Democrats say our leaders should prioritize climate change while very few Republicans agree. Republicans are more likely than Democrats to say we should focus on supporting Israel, limiting immigration, and blocking the flow of illegal drugs into the country.

These disagreements are normal and healthy, and they should lead to vigorous debate. If America is going to serve as an example of democracy to the world, we need to show that we can disagree and do so publicly. The political process, which will always include partisanship, is the way we settle our differences.

But hopefully we can agree that our national interest should come before party interests. Vandenberg’s maxim is worth remembering, even if we don’t always follow it.        

Lee Hamilton, 93, is a senior advisor for the Indiana University (IU) Center on Representative Government, distinguished scholar at the IU Hamilton Lugar School of Global and International Studies, and professor of practice at the IU O’Neill School of Public and Environmental Affairs. Hamilton, a Democrat, was a member of the U.S. House of Representatives for 34 years (1965-1999), representing a district in south-central Indiana.

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