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The showdown on trade in Congress, explained

The House is locked in a tense showdown over a series of trade bills that have divided both parties and pitted Obama against progressives and labor groups.

The House is locked in a tense showdown over a series of trade bills that have divided both parties and pitted President Barack Obama against progressives and influential labor groups.

High-profile administration officials — including White House Chief of Staff Denis McDonough, Labor Secretary Tom Perez and Treasury Secretary Jack Lew — met behind closed doors with House Democrats Thursday as backers of the president's trade agenda scrambled for sufficient support to keep Obama's plan for a trade agreement with Pacific Rim nations alive.

RELATED: ‘Fast track’ vote set for Friday

It's a complicated process full of acronyms, partisan divisions and a domino-like series of votes that could be stopped or derailed at almost any time. So here's what you need to know about the next few days:

What exactly does the president want?

The overall deal, called the Trans Pacific Partnership, or TPP, would expand U.S. trade relationships with more than a dozen Pacific nations. Obama has argued that the agreement would inject a new global vitality into American markets and boost job creation.

To get to a deal, the administration is pushing for Trade Promotion Authority (TPA) — commonly known as "fast-track" authority. If Congress approves, the president would be able to negotiate a trade deal with other countries without Congress amending it.

Wait, why would Congress give up its ability to amend a bill?

Backers of fast-track authority argue that the president of the United States should be the sole U.S. entity negotiating a complex deal with other nations, without 535 members of Congress meddling with the specifics. If "fast-track" authority on trade passes, once the White House secures a deal, the president can bring it to Congress for an up or down vote, without any changes and with limited debate.

RELATED: Obama, GOP lawmakers allies on trade bills

Would this apply just to Obama, or to future presidents, too?

Good question! Fast-track authority will apply for the next six years, so it will impact the next president. But giving the authority to Obama is one reason why some at least conservative Republicans aren't on board with it. These conservatives don't want to be seen as giving a president even more authority when their constituents are already accusing the president of executive overreach on issues like immigration and health care. However, the majority of Republicans are backing Obama on this measure, saying that the expanded trade would be good for U.S. businesses.

Most of the time, when conservatives are upset about something, progressives are all for it -- and vice versa, right? So why are some Democrats so upset about all this?

Progressive Democrats like Sen. Elizabeth Warren and powerful labor groups like the AFL-CIO see major multinational trade deals as a step towards further outsourcing by major corporations at the expense of U.S. workers. Warren even said last month that the Trans Pacific Partnership would be "just another tool to tilt the playing field in further of multinational corporations and against working families."

Obama shot back that Warren is "wrong on this."

Are there any changes to the trade bill that might make Democrats feel better about it?

Maybe. The House is scheduled to vote on Friday on a measure called the Trade Adjustment Assistance (TAA) bill. That legislation is intended to shield workers who might be adversely affected by the trade deal.

The vote could potentially be quite close.

House Minority Leader Nancy Pelosi and Speaker John Boehner have worked on some compromises that could win more Democratic support, but there are still a few outstanding issues that Democrats fear would leave workers unprotected. While some Republicans, especially those from Rust Belt states, are in favor of the legislation, Democrats are probably going to have to unite to get it over the finish line. And the most vehement opponents of the trade agreement, including the AFL-CIO, are urging members to vote against it, saying that defeating the Trade Adjustment Assistance measure would be the fastest way to scuttle the whole deal.

RELATED: House Democrats express concerns over controversial trade bill

So TAA +TPA = TPP? This sure is a lot of acronyms.

Seriously.

So what's actually going to happen next?

If the Trade Adjustment Assistance measure doesn't pass on Friday, everything else will grind to a halt, at least for a while.

House Majority Leader Kevin McCarthy has said that Republicans won't bring the "fast-track" legislation up for a vote if Trade Adjustment Assistance legislation fails.

It's going to be an extremely close vote; no one is exactly sure what will happen.

If the Trade Adjustment Assistance legislation passes, the "fast-track" measure will come up for a vote on the House floor.

That will also be a close vote.

Leadership sources indicate that there are about 160-190 Republicans on board and as many as 20 Democrats, but those numbers could be in flux as lawmakers are buffeted on all sides by advocates across the ideological spectrum who are trying to sway them.

And if the fast-track legislation also passes, an up-or-down vote on the overall trade deal will likely come up this fall.

Whew!

RELATED: Why Obama’s trade proposal is a tough sell: Americans want to protect jobs

What does Hillary Clinton think of all this?

The Democratic frontrunner has said only that any trade agreement must "produce jobs and raise wages and increase prosperity and protect our security," and she hasn't taken a definitive stance on TPP or any of the other associated legislation.

This is a tricky issue for her—after all, it was President Bill Clinton who helped get NAFTA through Congress back in 1994.

On Thursday, one of her Democratic presidential opponents, Sen. Bernie Sanders of Vermont, was not shy about blasting her for failing to weigh in on the issue.

"Trade policies have been disastrous," he told reporters. ""If she's against this, we need her to speak out, right now."

NBC News' Carrie Dann contributed reporting. This article originally appeared on NBCNews.com.