The Senate is poised to vote this week on fast-tracking the Trans-Pacific Partnership trade deal. Economentator Tyler Cowan begs people to keep the big picture in mind:

I say let’s just have a two-way button and ask everyone to press it: do you believe that TPP would lead to a net gain in economic welfare or not?
If those costs and outrages associated with TPP are so bad, it ought to be possible to do a study which makes the trillion in benefits go away. Has anyone done such a study? Would such a study survive the commentary from the NBER annual macro conference?
I am not suggesting that economic welfare should be the only criterion for evaluating a policy. But making everyone press this two-way button — and in the process citing their favorite comprehensive policy study of TPP – would do wonders to bring clarity to the debate. Commentators still would have the liberty of accepting the reality of the economic gains while disfavoring the policy, as indeed I do with forced kidney extraction and transplant.
In the meantime, the more desultory lists I see of possible negative consequences of TPP, the more likely I am to think it is a good idea after all.

Critics have shown some remarkable ingenuity getting around Cowan’s essential challenge. Sen. Elizabeth Warren (D-Mass.) has concocted an improbable narrative in which one provision of the trade deal might allow companies to gut all sorts of regulations, such as the Dodd-Frank financial reforms. By her reasoning, then, the deal could lead to all sorts of economic damage that traditional economic analysis doesn’t account for. Sure, her nightmare scenario is theoretically possible. But it’s also too remote to weigh strongly on the negative side of the ledger.

Paul Krugman admits the TPP might bring net economic benefits, but he argues that they are smaller than the analyses suggest, in part because the deal’s intellectual-property provisions will reduce potential growth abroad. But, Brad DeLong asks, where are the numbers showing that the net effects of those provisions would be so negative that they make the deal unattractive? Cowan, meanwhile, notes that there are costs and benefits for developing countries that adopt first-world intellectual-property protections.

Vox.com’s Dylan Matthews has the most appealing criticism of the TPP thus far. The problem, he argues, isn’t that the trade deal would force Americans to compete with poorer and more desperate workers overseas. The problem is that the deal wouldn’t do enough of that. Trade helps poor nations develop without exacting net economic damage to rich nations, but the poorest countries are left out of the TPP. Trade deals should instead be as wide as possible, negotiated under the World Trade Organization and not limited to a handful of TPP countries. This is a fair point, but stopping the TPP, particularly now, would make domestic and international circumstances less favorable to negotiating broader agreements in the future.

For its part, the White House argues that many of the critics’ concerns are overblown, and it points out that it has geostrategic considerations as well as economic ones on its side: Ditching the TPP would enable China to build the multilateral trade and political blocs it would like to see in Asia.

Still, Krugman asks, why push the TPP when doing so risks “alienating labor” and “disillusioning progressive activists?” This is a dangerous line of thinking, suggesting that mere partisan solidarity is a legitimate reason to oppose the trade deal. It might also explain why he and other savvy thinkers are spending a lot of energy concocting justifications for opposing the TPP that don’t also make them seem reflexively, untenably anti-trade.

Constricting the political space for progressives to favor trade deals, which is a potential result of the current debate, would be resoundingly bad for the country and the world, making it much more difficult to further liberalize economic exchange and encourage positive-sum international cooperation. If the term “progressive” is to bear any rational relation to its dictionary definition, this cannot happen.

UPDATE, 10:45 a.m.: Text above slightly edited for clarity.