Democratic presidential nominee Hillary Clinton gives a speech on the economy after touring Futuramic Tool & Engineering in Warren, Mich., on Aug. 11. (Andrew Harnik/Associated Press)

DEMOCRATIC PRESIDENTIAL nominee Hillary Clinton traveled to Michigan on Thursday, using the quintessential Rust Belt state as a setting to talk economics, just as Republican nominee Donald Trump had done a few days earlier. There was much to agree with in Ms. Clinton’s riposte to Mr. Trump, particularly her emphasis on the progress the U.S. economy has made since the Great Recession, a fact that election-year rhetoric generally glosses over, especially in Mr. Trump’s alarmist portrayal of the Obama administration’s economic record. The Democrat was correct when she noted that the Republican’s tax plans overwhelmingly favor upper-income households. Exploring relatively unconventional ground, she called for greater support of vocational training, contrary to the “commonplace view, which is everybody needs to go to college.” More than half of jobs projected to come open in 2020 do not require a degree, she said.

For the most part, however, Ms. Clinton did not venture beyond the usual Democratic talking points: higher taxes for millionaires, equal pay for women, expanded Social Security and so on down the familiar list. Absent from her speech was any discussion of the persistent sluggish trend in U.S. productivity, which has fallen for the past three quarters after growing at a historically subpar rate of 1.3 percent from 2007 through 2015. Increasingly, economists name this as the greatest long-term threat to growth, and it would be nice to know, specifically, what Ms. Clinton proposes to do about it beyond investments in infrastructure and education.

One thing she was definitive about was trade, specifically the Trans-Pacific Partnership, which she touted as secretary of state but denounced Thursday: “I oppose it now. I’ll oppose it after the election, and I’ll oppose it as president.” This leaves supporters of the 12-nation tariff-slashing deal clutching to the thin hope that she does not really mean what she says; but her distinction between “after the election” and “as president” implied that she would not even countenance approval of the TPP by a lame-duck Congress if she wins on Nov. 8. In short, there’s a disconnect between Ms. Clinton’s protestation that, unlike Mr. Trump, she does not fear global competition and won’t “rant and rave or cut ourselves off from the other side of the world” — and her actual policy proposals. She may not rant and rave, but she does want to create a new trade “prosecutor” to deal with nations that purportedly cheat the United States, as well as exact financial penalties from U.S. firms that move production abroad. Would Mr. Trump disagree?

Among the many discouraging consequences of this extraordinary political year, none is more ominous than the rise of protectionist sentiment in both parties, as encouraged by Mr. Trump and by Ms. Clinton’s former Democratic rival Bernie Sanders. With but 5 percent of the world’s population, the United States needs robust engagement in markets abroad. That will be impossible under political leaders who regard such engagement as a zero-sum proposition — or who understand the reality but decline to make the case for it to the American people.