Wyden’s staff tweeted a link to a video in which his Republican counterpart, senator Orrin Hatch, promises to work bring those bills to the floor together. Hatch, meanwhile, complained that Obama failed to bring his own party in line. And he said that Democrats were re-casting his expression of bipartisan goodwill as an ironclad commitment, effectively to find an excuse to bow to pressure from the left.

The pressure came mainly from a group of senators, led by Massachusetts’ Elizabeth Warren, who fear that giving the White House trade-negotiating powers will make it easier for corporate interests to push back against domestic regulation. This vote is another reminder of the populist Warren’s ability to move her party, even against a sitting president; indeed, Warren’s stand has contributed to Hillary Clinton’s ambivalence on trade, which left Obama exposed.

But it doesn’t explain why trade-loving Democrats backed off the bill. For that, you have to go back to the purpose of the TAA.

Democrats who support trade understand that it has costs and benefits. Even if they don’t buy Warren’s critiques about corporate empowerment—they might note that the US has never lost in trade arbitration with a corporation—they fear for the workers who will lose their jobs and require assistance as the economy responds to new trade rules. That’s why they wanted the TAA, which in its current form would provide unemployment benefits and skills training to those who could provide evidence that newly lowered trade barriers led to the loss of their jobs, attached to the trade-negotiating authority.

So why wouldn’t the Republicans commit to making it part of the package?

“It would gain Democrats in Senate, [but] complicate efforts to move bills through the house due to House Republican opposition” to TAA, a Democratic Senate aide said. Indeed, the measure isn’t expected to be incredibly effective, and it triggers the conservative reflex against government aid. But that’s exactly why Senate Democrats want more assurances that Republicans will back such transition aid after (or if) it passes their chamber.

Republican leaders say they will bring the bill back to the floor soon, but it’s not clear how they will woo the Democrats they need without committing to more robust aid.

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