Had the first presidential debate been a boxing match, Hillary Clinton would not only have been comfortably ahead on the judges' score cards, she'd have been awarded a technical knockout if the referee had noticed her opponent's labored arguments by the final round. But before her supporters get too carried away celebrating, they would be wise to review the Democrat's early performance, which was not championship caliber.

As well prepared as the former secretary of state, senator and first lady may have been on issues ranging from foreign policy to income inequality and police-community relations, she seemed flummoxed at the outset when Donald Trump brought up foreign trade deals like the North American Free Trade Agreement (NAFTA) and the Trans-Pacific Partnership. The issue came up in the context of job creation, and Mr. Trump's attack was a familiar one — a claim that the federal government under President Barack Obama and others before him allowed vital manufacturing jobs to be exported out of the country.

“All you have to do is look at Michigan and look at Ohio and look at all of these places where so many of their jobs and their companies are just leaving,” the Republican nominee growled. “They're gone. And Hillary, I'll ask you just this: You've been doing this for 30 years. What are you just thinking about these solutions just now?”

This kind of flawed reasoning should have been corrected by Ms. Clinton. Free trade is good for economic growth, not bad. That used to be a bedrock Republican belief. And many of the job losses credited to agreements like NAFTA are jobs that would have left the country anyway — if not to Mexico, then perhaps the Far East. That's simply the nature of a modern global economy as manufacturers seek to lower costs, particularly using low-wage labor.

The United States isn't going to beat the world in the low-wage labor market, nor should it. The U.S. has its own advantages in job growth, and they include higher worker productivity and better information technology, transportation networks and education. When the nation plays to those strengths it can create economic powerhouses like Google and Apple. Setting up barriers to foreign trade to keep legacy manufacturing jobs that no longer make economic sense only raises consumer costs, increases tariffs and sets off trade wars.

But that wasn't Ms. Clinton's response in the debate. Instead, she denied supporting the Trans-Pacific Partnership, claiming that her description of it as a “gold standard” of trade agreements was in the context of “hoping” it would be a good trade deal. That's a bit of rewrite of history and made the Democrat appear to have casually flip-flopped on the TPP — and then lied about it.

The politics are clear enough. Voters in swing states like Ohio, Pennsylvania and Michigan where job losses overseas are a big issue could decide this contest. But the electorate at least needs a grown-up conversation about trade. It certainly isn't getting one now — and probably won't given that neither candidate supports the TPP. Yet whoever is elected in November, the country is going to have to do something about trade and particularly as it relates to China. Should Congress reject the TPP, U.S. economic influence in the region will wane — and that's a problem not only for the economy but for national security.

What the Democrat should be saying is that foreign trade is a relatively small component of the economy and that those jobs that have been lost overseas over the last 30 years aren't coming back. What the nation needs to do now is focus on creating good-paying jobs, not by erecting trade barriers but by taking steps to encourage growth — invest more in public infrastructure, nurture small businesses, encourage innovation, provide more job training and improve access to capital. What you don't do is rewrite the tax code to provide a $1 trillion handout to the wealthy, which is what Mr. Trump has proposed.

Ms. Clinton doesn't necessarily have to defend 22-year-old trade agreements as if this was 1992 and she was running against Ross Perot. She needs to convince the public that she has better ideas about creating jobs right here and right now. That didn't come across Monday night, and it needs to be revisited when the two candidates meet again Oct. 9 in St. Louis.