COMPETITIVE CHINA-BASHING has become a quadrennial ritual in U.S. politics. In 2008, President Obama beat Republican John McCain, partly by promising to “go to the mat” with China over its trade practices. In office, he, like his predecessors of both parties, abandoned confrontation in favor of a broadly pragmatic approach. This time around, it’s presidential challenger Mitt Romney promising to “crack down on China,” specifically by labeling the People’s Republic a “currency manipulator” on his first day in office. Time will tell whether and how Mr. Romney follows through, if he wins — but we wouldn’t be surprised if he, too, governed differently from how he campaigned. That’s the first reality to keep in mind as the two candidates quarrel over who invested more of his own money in China.

And here is a second one: China is not quite the unstoppable threat to U.S. prosperity that you hear about in crowd-pleasing rhetoric. Undoubtedly, China has grown explosively over the past two decades, capturing a huge share of world trade. But more recently, the story out of China is about a corruption-plagued communist state struggling to escape what economists sometimes call “the middle-income trap.” Export-led growth has given way to an investment boom that’s looking more and more like a bubble. Though the United States still had a $295 billion trade deficit with China last year, our indebtedness to the nation declined — while U.S. productivity gains made manufacturing here more cost-competitive. These trends are also at least partly linked to the fact that, during the past two presidential terms, China has allowed its currency to appreciate 37.5 percent against the U.S. dollar in real terms.

So when Mr. Romney promises to declare China a currency manipulator, he is pledging to escalate a battle that the Obama administration is fighting reasonably well, if less dramatically. The good news is that the declaration would be mostly symbolic — the first step in a long negotiating process that might or might not culminate in a change in China’s policy.

U.S. penalties might prove counterproductive, as the Obama administration has already shown with an exception to its pragmatism — the slapping of tariffs on imports of low-priced Chinese tires. Mr. Obama boasts of that measure on the campaign trail. But economists at the Peterson Institute for International Economics estimate that the 1,200 jobs saved cost consumers $1.1 billion in higher prices in 2011 — almost $1 million per job.

China has given the United States many legitimate causes of complaint, from its human rights violations to its incessant intellectual-property theft to its saber-rattling against democratic neighbors. If Mr. Romney has it in mind to continue challenging China on those fronts, we agree. But the U.S. and Chinese economies are far too deeply intertwined to risk a trade war over currency imbalances that are gradually adjusting through peaceful means.