A TOP priority for President Trump in what’s left of this session of Congress is a vote in the House of Representatives on his trade deal with Mexico and Canada. Passage in the Republican-controlled Senate is all but certain, and, because trade interests don’t track precisely with partisan ones, there would probably be a bipartisan majority for it in the Democratic-controlled House, too — if Speaker Nancy Pelosi (D-Calif.) brings it to the floor. Should she?

A certain naked but understandable political calculation says she should not. Democrats’ primary goal is to resist Mr. Trump; a trade victory could help his 2020 campaign. Better, on this view, to stick to Ms. Pelosi’s current approach — insisting on modifications to the proposal’s labor, environmental and pharmaceutical provisions, and discussing them with Mr. Trump’s trade representative, Robert E. Lighthizer — indefinitely.

The problem is that Mr. Trump might revive his threats to withdraw from the existing trade framework, the North American Free Trade Agreement, damaging the hemispheric economy. Yes, Mr. Trump would bear primary responsibility; indeed, he’s responsible for insisting on renegotiating NAFTA in the first place. On balance, though, it’s better not to gamble with people’s jobs and income, even for an understandable political reason, unless overriding substantive policy concerns justify it.

They don’t. In one respect — updating rules for cross-border e-commerce, which was still in its infancy when NAFTA took effect 25 years ago — Mr. Trump’s deal is a real improvement over the status quo. For the rest, it mostly leaves NAFTA intact, or changes it in ways Democrats and their union allies have long demanded, especially by increasing the amount of U.S.-made inputs that cars and trucks would need to qualify for tariff-free trade among the three countries. What’s more, Mr. Trump negotiated access to a greater percentage of Canada’s notoriously closed dairy market. Neither the auto nor dairy provisions have much to do with free trade — “managed trade” would be a better description. But Democrats can’t really object, given their past positions. In fact, sending Mr. Trump’s deal down to defeat could have political costs for Democrats, too — specifically, in House districts where farmers and other interests support the deal, and in the auto-making state of Michigan, pivotal for the presidential election.

As for the Democrats’ expressed objections to the enforcement provisions for labor and environmental rules, or to what they decry as unduly long patent protections for the makers of brand-name drugs, similar objections have been raised to other trade deals in the past, and Ms. Pelosi found compromises. She could do so again.

The United States is embroiled in an all-fronts trade war with China. Whether Mr. Trump is pursuing it the right way — we think he isn’t — or not, its necessity is far greater than that of fights he has picked with other partners, such as South Korea, Europe, Japan, Mexico and Canada. To put out the NAFTA fire, even if it’s a blaze Mr. Trump fanned, would help stabilize the global economic outlook and focus U.S. attention on China.

Read more:

Rob Portman: USMCA is a needed upgrade from NAFTA. Let’s get it passed.

Marc A. Thiessen: If they won’t pass his trade deal, Trump should make Democrats own NAFTA

Mike Pence: Congress must pass the U.S.-Mexico-Canada Agreement

Greg Sargent: The 2020 Democrats just made a move on a big Trump weakness

Stan Greenberg: Trump promised a new trade policy. But his new NAFTA might be worse than the old one.