Now that Congress has approved Trade Promotion Authority legislation giving President Obama the power to negotiate trade agreements that can't be amended by Congress, a new pact between the United States and 11 Pacific Rim nations is expected to be completed in the coming months.

But path for the Trans-Pacific Partnership to become law could be just as bumpy as passing the trade promotion bill, thanks to a looming election year and opponents in Congress who aren't ready to abandon the fight against new trade deals that they believe will damage the American economy.

House Minority Leader Nancy Pelosi, D-Calif., who led her caucus in an effort to sink the trade promotion deal, sent a signal in June that she's not done fighting and will not endorse a Pacific Rim trade pact that doesn't include certain provisions concerning worker rights and environmental protections.

"I think that the more public support we have for our position, and the leverage we will have, we will be taking it to the public," Pelosi said when asked about the looming deal.

The Trans-Pacific Partnership has been in the works for half a dozen years. It's a wide-ranging agreement that would slash prohibitive tariffs and set down a broad array of rules and regulations governing trade, including environmental standards and intellectual property enforcement. Its completion was dependent on the TPA deal, since U.S. trading partners tend not to agree to conclude deals until it's clear that Congress only has an up-or-down vote on these agreements.

Many of the details of the deal are still unknown or are being kept secret in a Capitol room where lawmakers can read it, but can't remove copies or take notes on what is in the deal. Trade experts predict a final deal could be months away, by Sept. 30 at the earliest and perhaps not until the end of the year.

At that point, the deal mandates months of review by Congress and the International Trade Commission, which is required to issue a report on the deal's potential economic impact. Only after the extensive review period will lawmakers be able to hold an up or down vote on the agreement.

By some estimates, if the Trans-Pacific Partnership isn't finalized until the end of the year, the months-long review could delay its arrival in Congress until just before the 2016 elections.

"Congress isn't going to vote for it then," Dan Ikenson, director of Cato's Herbert A. Stiefel Center for Trade Policy Studies, told the Washington Examiner, citing election-year politics.

So Congress would likely wait until the so-called lame duck session that convenes in November, after the election. And if the trade deal misses that window, Ikenson warned, "Then it goes to the next president."

That's no problem if one of the leading Republican candidates wins the White House. But Hillary Clinton, the leading Democratic presidential candidate, has sided with Pelosi in her skepticism of new trade deals.

Clinton's trade perspective tracks her overall move to the Left, in part because of more liberal candidates like Sen. Bernie Sanders, I-Vt., who calls the TPP, "a disastrous trade agreement designed to protect the interests of the largest multinational corporations at the expense of workers, consumers, the environment and the foundations of American democracy."

"I suspect she'll be campaigning against the trade agenda," Ikenson said of Clinton.

So passage of the Trans-Pacific Partnership, six years in the making, may hinge on what happens in the next few months. "There's very little time to spare if Obama wants this done on his watch," Ikenson said.