There are good reasons to oppose the Trans-Pacific Partnership, the big Asian trade deal the Obama administration is hoping to finalize soon. I lean against it, mostly because it could hurt poor countries left out of the pact (notably Bangladesh and Cambodia), and because I think trade liberalization should be happening globally through the WTO rather than in piecemeal regional agreements.

But it's hard to sympathize with the arguments Sen. Bernie Sanders (I-VT) put forward in his statement Tuesday, celebrating the Senate's rejection of a bill that'd enable final approval of the pact without congressional amendments:

A major reason for the decline of the American middle class and the increase in wealth and income inequality in the United State is our trade policies - NAFTA, CAFTA and Permanent Normal Trade Relations with China. This agreement would follow in the footsteps of those free trade agreements which have forced American workers to compete against desperate and low-wage workers around the world – including workers in Vietnam where the minimum wage is 56-cents an hour.

Sanders is suggesting that TPP would be bad because it would force US workers to compete with workers in Vietnam — implicitly, that it's bad because it expands economic opportunity for poor workers in Vietnam at the expense of significantly richer workers in the United States.

The factual basis for this claim is pretty dubious. Even economists who think trade has significantly hurt US manufacturing workers tend to think the damage is already done, and that future trade deals will involve sectors of the economy in which the US does more exporting than importing (namely, services and agriculture). Moreover, insofar as the deal would advantage imports, that would lower prices for US consumers, particularly poor and middle-class consumers for whom spending on manufactured goods and clothes eats up a bigger share of income. And how much it expands opportunity in Vietnam depends a lot on the specific "rules of origin" in the deal.

But even if the deal did, on net, hurt American workers, Sanders is implicitly arguing that it's worth impoverishing desperately poor people abroad so that far richer people in the United States can be slightly better off. I don't think Sanders bears any ill will toward developing-world workers; he's consistently supported raising labor standards abroad, and during the debate over CAFTA he explicitly stated that he thought the deal would be a "disaster for the people of Central America," as well as for the US.

But he's simply mistaken about what's best for the developing world. "Forc[ing] American workers to compete against desperate and low-wage workers around the world" is not just good for those "desperate and low-wage workers"; it's actually a demand placed on developed countries by the UN Millennium Development Goals, which call for "tariff- and quota-free access for Least Developed Countries' exports." No members of the official least developed countries list are actually part of TPP — they're even poorer, and thus, on Sanders's logic, more dangerous as trading competition to the US.

When you talk to development experts who focus on trade, like the Center for Global Development's Kimberly Ann Elliott, the one point they press on again and again is the need for DFQF — duty-free, quota-free — access to rich countries' markets for exporters in least developed countries. There's been progress on this front. Through the Everything but Arms program, the European Union provides DFQF access to non-arms imports from least developed countries. In 2005, rich countries in the WTO committed to providing DFQF access to at least 97 percent of products. Through the African Growth and Opportunity Act, the US provides duty-free (but not quota-free) access to the US market for many sub-Saharan African nations. But the goal of completely free exports from all least-developed countries to all rich countries is still not reached, both because certain sensitive products (particularly in agriculture) are exempted from its benefits and because, in the US's case, many poor countries are left out of the deal.

A true anti-poverty trade agenda would be the exact opposite of what Sanders wants. It would directly put US workers in competition with more — and poorer — workers abroad. The effects on US workers would likely be small, but even if they weren't, that trade is worth making. Fighting desperate poverty in the developing world is more important than marginally boosting the US middle class. And there are many, many ways to help the American middle class that don't involve keeping the world's poorest people in a state of total immiseration.