MEXICO CITY — Everyone here wants to know what’s going to happen to Nafta — the North American Free Trade Agreement, which has closely linked the economies of Mexico, Canada and the United States for more than two decades. Donald Trump has described Nafta as the “worst trade deal ever made.” But will he actually destroy it?

Until just a few days ago I was pretty sure that he wouldn’t. My guess was that he would negotiate some minor changes to the agreement, declare victory and move on. Markets seemed to agree: The Mexican peso plunged after Trump’s election but then rebounded, effectively reaching the verdict that nothing terrible would happen.

But I’ve been revising that view in light of recent events — especially Trump’s health care temper tantrum. Breaking up Nafta would be terrible for Mexico and bad for the U.S. It would horrify major U.S. business interests, which have spent two decades building their competitive strategies around an integrated North American market. But it might be good for Trump’s fragile ego. And that’s a reason to fear the worst.

Let’s start by admitting that Nafta, although it led to rapid growth in both Mexican exports to the U.S. and U.S. exports to Mexico, hasn’t lived up to the expectations of some of its proponents.