The hottest policy fight in Washington might be between President Biden and Vice President Harris. The conflict is over whether businesses should invest here in the United States, or south of the border in Central America.

The stark contrast between Biden’s America-first approach and Harris’s free-trade advocacy was visible on the afternoon of Wednesday, July 28. At 2 p.m., Mr. Biden spoke at a Mack truck manufacturing facility in Macungie, Pennsylvania.

“Today, I’m here to talk about a commitment that’s sacred to me and central to our efforts to keep things moving. It’s a straightforward solution: support and grow more American-based companies,” Mr. Biden said. “Put more Americans to work in union jobs. Strengthen American manufacturing and secure critical supply chains… I can sum it up in two words: Buy American. Buy American.”

At 4 p.m. the same afternoon, “senior administration officials” were briefing reporters about efforts by Vice President Harris to “address the root causes of immigration” from Central America. Said the senior administration official: “the Vice President issued a call to action to the private sector, getting some of our most prominent corporations to commit to make investments and also to provide philanthropic support into the region.”

On July 29, Ms. Harris unveiled a “U.S. Strategy for Addressing the Root Causes of Migration in Central America.” In a “cover message from Vice President Kamala Harris,” she wrote, “While, in the past, the private sector has been an underutilized partner, our Administration is calling on U.S. and international businesses to invest in the region — and thus far, 12 have done so.”

A May 27 White House fact sheet listed Microsoft, Chobani, Mastercard, and Nespresso as among the companies joining Harris in a “Call to Action.” The fact sheet said that “near-term private sector commitments will be mutually reinforced by sustained U.S. government efforts to foster a business-enabling environment, increased private sector investment, and sustainable economic growth and opportunity.”

Rhetoric aside, neither Mr. Biden nor Ms. Harris seems deeply ideologically committed to the side they’ve chosen in this conflict. As a senator in 1993, Mr. Biden voted for the North American Free Trade Agreement. Ms. Harris has said she would have opposed it.

Economists and free-trade advocates will argue that it isn’t a zero-sum game. When companies like Microsoft or Mastercard invest in Guatemala, Honduras, and El Salvador, the prosperity that is created winds up helping Americans by creating customers for other American companies and cheaper products for American consumers, while reducing the costly chaos of illegal immigration.

That rising-tide-lifts-all-boats theory of international trade, though, is rejected by the Joe Biden of 2021, or at least by whoever is writing his remarks. At the Mack truck assembly facility, Mr. Biden faulted previous presidential administrations for waiving “Buy American” requirements for federal purchases. “You can’t give exceptions,” the President said. “Then they can’t take the jobs overseas.”

Mr. Biden said he is changing the rules so that the amount of domestic content required for a “Made in America” qualification will rise to 75% from 55%. “Yes, we’ll keep trading with our allies, but we need to have a resilient supply chain of our own so that we’re never again at the mercy of other countries for critical goods ever again. Ever,” Mr. Biden said.

Vice President Harris is making the case that more jobs in Guatemala, Honduras, and El Salvador will be good for workers in California, Texas, Wisconsin, and Pennsylvania. Mr. Biden’s comment about “take the jobs overseas” implies the opposite — what seems plain to many people in American cities and towns that have seen factories close and good-paying union manufacturing jobs disappear to China or Mexico.

The Democratic divide on trade dates back to at least the 1990s, when a free trader, Vice President Gore, faced off against a protectionist congressman, Richard Gephardt. The issue also splits Republicans. Figures such as Donald Trump and Patrick Buchanan are more skeptical of international trade agreements, while others, such as Presidents Bush and Mitt Romney, are less anxious about loss of American jobs overseas.

In a non-election year like this one, Mr. Biden and Ms. Harris can get away with tailoring different messages to different audiences. Mr. Biden can tell Pennsylvania voters that “Buy American” is a “sacred commitment.” Hours later White House aides can brief Washington and New York reporters about the pleas by Vice President Harris to have American companies invest in Central America.

If, come election season, it turns out that the Biden-Harris administration was better at creating jobs in Central America than in middle America, there will be a price to be paid at the polls. That it’s Mr. Biden talking “Buy American” in Pennsylvania truck factories while Ms. Harris is working on getting Microsoft and Mastercard to invest in Central America may be one sign that it’ll be Mr. Biden, again, at the top of the Democratic ticket in 2024.