On trade, John Boehner, Mitch McConnell, and President Obama are all hoping that the second time will be the charm.

What the three leaders have before them is a complicated maze of bills and political alliances that if properly navigated could give all three one of their biggest victories of this congressional session, not to mention the fulfillment of a major campaign promise that gave McConnell his majority: passage of the Trans-Pacific Partnership treaty with a dozen Asian and Pacific countries.

After failing to pass two of the preliminary measures through both chambers last month, Boehner and McConnell agreed to try again, this time breaking up the bills into separate votes, while promising passage of both.

The House provided a small glimpse at victory Thursday, passing one of the four trade bills, Trade Promotion Authority, which allows Congress to approve the so-called "fast-track" deal without amendments, acknowledging that any changes could destroy the 12-nation agreement. That legislation now heads to the Senate, where around a dozen Democrats will be needed to send the bill to the president's desk. A procedural vote is expected Tuesday.

For now, Senate Democrats are staying mum on how they'll vote. Fourteen of their members voted in May to proceed with TPA when it was still attached to the Trade Adjustment Assistance bill, which would provide assistance to workers hurt the trade agreement. Boehner and McConnell vowed last week that they would bring up and pass TAA shortly after clearing TPA through Congress, but pro-trade Democrats in the Senate must now decide whether they can take the Republican leaders at their word.

Given that the TPA-TAA package passed with just two votes to spare, Republican leaders will need many of those members to go along with the TPA bill next week.

If TPA becomes law without assistance for displaced workers, pro-trade Democrats argue that it won't look good for their party.

"The president's going to sign TPA," Sen. Thomas Carper of Delaware said. "That's going to happen. And when he does, we're going to look pretty foolish if we don't, as Democrats especially, make sure that we provide assistance to folks who might need it."

They have reason to be skeptical. Many conservatives in the House have no interest in passing TAA, particularly once TPA has made it to Obama's desk. And despite his assurances, it's unclear whether Boehner will have the votes to pass it without them.

Still, Sen. Dianne Feinstein, who supported the last trade package, said Thursday that she believed the Republican leaders were working in good faith. But the California Democrat would not say how she will vote on TPA next week, underlining that McConnell has not yet told Democrats how he will bring up TAA and assure passage of both bills.

"We have to figure out a way that nothing gets signed until TAA is on the president's desk," Feinstein said Thursday.

Several pro-trade Democrats met at the White House on Wednesday to discuss the issue with Obama, who has been vigorously lobbying on the issue, but they returned to the Capitol in the afternoon tight-lipped.

Asked about the White House tête"“à"“tête, Sen. Patty Murray deadpanned Wednesday: "What meeting?"

Sen. Ron Wyden, the top Democrat on the Senate Finance Committee, said Thursday that pro-trade Democrats have been meeting "almost nonstop" amongst themselves and with their Republican counterparts.

"I think everybody is being straight with each other. We've told them what is important to us," Wyden said. "I don't relate what they say because you can't negotiate on the subway in the Capitol. But what I'll tell you on the basis of discussions that went very late last night and into this morning the pro-trade Democrats feel very strongly about being able to make sure that all four of the bills actually happen."

On Thursday, Sen. Ben Cardin would not say how he would vote on the TPA bill.

The Maryland Democrat emphasized that he wouldn't automatically reject a piecemeal approach, but reiterated that he and other pro-trade Democrats would like to see it recoupled with TAA, the African Growth and Opportunity Act, and a customs enforcement bill.

"I'm going to wait to see what Sen. McConnell does in his conversations with us. I'll wait to see how they'll do it, but my position's been clear from the beginning, I want them all together," Cardin said. "I want to make sure that everything ends up on the president's desk."

Cardin couldn't say if pro-trade Democrats would vote as a bloc to support any procedural path forward. "We'll wait to see when it comes over how they decide to bring it up," Cardin said.

Given their leverage in the fight to pass TPA, some pro-trade Democrats now are calling on Republican leaders to include a vote to reauthorize the Export-Import bank alongside the trade bills. The authority for the bank is set to expire at the end of the month, something many conservatives in both chambers would like to see happen.

"We have not seen a complete package and just as we were very sure that we needed to have a path forward [for all four bills]. I'd love to see this as an opportunity to do something at least to avoid the charter for the Ex-Im bank to expire" Sen. Heidi Heitkamp said Thursday. "This is a high priority when you talk about trade. You can pass all the trade laws you want, but if you don't have trade financing, you don't have a trade policy."

"I think it's a good idea, but there's not an agreement to do that that I know of," said Sen. Tim Kaine, another pro-trade Democrat who could be needed to pass TPA.


Rachel Roubein and Alex Rogers contributed to this article

We want to hear what you think about this article. Submit a letter to the editor or write to letters@theatlantic.com.