The conventional wisdom on presidential elections is that foreign policy doesn’t play a decisive role — and most Democratic presidential candidates have largely avoided it so far. But in the 2020 presidential contest, foreign policy will feature more prominently than ever, and Democrats ignore it at their peril.

In 2016, voters had a clear choice between a traditional foreign policy leader with tons of experience in Hillary Clinton and a candidate with no foreign policy experience who promised to radically change the way U.S. diplomacy was conducted. Although polls showed voters trusted Clinton more as a commander in chief, she lost the election, and President Trump has been implementing his new vision for the United States’ role in the world ever since.

That’s been a mix of what Trump calls “nationalism”: a pivot away from values-based foreign policy advocacy, an embrace of populism abroad, support for authoritarian rulers, skepticism of international organizations such as NATO, and unilateralism in confronting threats such as Iran and the rise of China.

Hatice Cengiz shares new details of her final hours with fiance Jamal Khashoggi before the Post opinion writer was murdered in the Saudi Consulate in Istanbul. (The Washington Post)

A new poll this week by the Democratic group National Security Action showed that Trump is vulnerable on foreign policy, even among his own supporters, especially when it comes to trade and Russia. And yet, Democratic presidential candidates — with a couple of exceptions — have remained quiet on these issues.

One exception has been former Maryland congressman John Delaney. He has been talking to voters about foreign policy since becoming the first Democratic candidate to declare his candidacy in July 2017. He is convinced it’s the most important 2020 issue.

“Foreign policy is the biggest part of the job. And that’s the irony of running for president,” he told me during an interview.

Delaney is running as an unabashed internationalist, centrist, moderate Democrat who believes in returning to the assertive, values-promoting, alliance-building foreign policy approach that majorities in both parties once traditionally supported. This month, he laid out a detailed agenda during a speech at the Johns Hopkins University School of Advanced and International Studies.

The Center for American Progress released a study this month that showed Democratic voters do care about foreign policy, though they want to hear about how it relates to their security and prosperity — not about “maintaining the liberal international order.”

Delaney argues foreign policy is more intertwined than ever with economics and prosperity at home, and that Trump has co-opted the legitimate grievances of those left behind by globalization to advance his unilateralist, nationalist, populist agenda. But Delaney believes Democratic primary voters can be persuaded to fix the system rather than blow it up.

“The world has changed very rapidly and profoundly, and we didn’t do the kind of things we should have done to prepare our citizens for this. As a result, a lot of them feel left behind and their response is to question everything,” he said. “The American people will allow you to think globally as long as they believe you are investing locally.”

Also, Democratic primary voters object to the way the president conducts himself on the world stage, Delaney said. Values, decency and morality are now foreign policy issues, as well.

That basic frame of a return to normalcy in foreign policy is similar to what the Democratic front-runner, former vice president Joe Biden, is running on, as well. But Biden has yet to articulate a specific foreign policy agenda, and when talking about China, for example, he has stumbled.

The two progressive candidates most active on foreign policy are Sens. Bernie Sanders (I-Vt.) and Elizabeth Warren (D-Mass.). They both want the Democratic Party to pursue a more progressive, less interventionist, less capitalist foreign policy that would represent a wholesale change, as opposed to the tweaks centrists are proposing.

The fault lines that would emerge if the Democratic primary did turn to a foreign policy focus are clear: the Trans-Pacific Partnership, the trade war with China, Israel, Venezuela, Iran, defense spending and perhaps Russia. The Democratic leadership in Congress has an interest in papering over these differences. When interparty differences emerge on Israel, for example, Republicans are quick to pounce.

Delaney argues that Trump’s nationalist tendencies and the negative results have pushed Democratic voters back toward a more centrist, traditional foreign policy position. It’s a fact that more centrist Democrat national security candidates were elected during the midterm elections in 2018 than progressives.

“We were trending toward isolationism as a party, in many ways. But Trump’s brand of nationalism is being rejected by many Democratic primary voters,” Delaney said. “That’s a positive step for the party.”

The truth is, we don’t know which foreign policy Democratic voters favor because they haven’t been presented with a clear and honest choice. In 2020, foreign policy will be on the minds of all Americans, and if Democratic presidential candidates don’t engage in the debate, they will lose it.

Read more: