Negotiators have finalized the Trans-Pacific Partnership (TPP), a complex trade deal between 11 Pacific countries that together make up about 40 percent of the global economy. The agreement will give the Obama administration a signature achievement if it’s approved by lawmakers.

Since spring, the Pacific trade negotiations have divided Democrats while finding support from most congressional Republicans, including Senate Majority Leader Mitch McConnell. Opponents on the left and right have a variety of fears about the TPP, ranging from its level of secrecy (the full text is unavailable to the public, though excerpts have been leaked online) to the belief that it could shift U.S. jobs overseas.

Chances are, the president will secure passage. In July, Congress voted to give Obama trade promotional authority (TPA), effectively allowing the administration to “fast-track” the deal toward a simple “yes” or “no” vote from lawmakers, without endangering the negotiations with domestic squabbles over amendments. The authority has benefited other presidents who have been able to pass controversial agreements.

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In the presidential campaign, the TPP separates the populists from the mainstream candidates. There has been no more vocal critic than Donald Trump. The real estate mogul has called the deal “an attack on American business.” Trump, who considers himself a world-class negotiator, has on several occasions stated (in fewer words) that America’s trade deals are negotiated by incompetents. His populist-nationalist rhetoric illustrates the two-pronged thrust of the anti-TPP conservatives: promise to keep American jobs at home and oppose anything that the president does.

Carly Fiorina merely said that she was “uncomfortable” with the deal back in May. Ben Carson has said that Americans should have a say in trade deals through their representatives, but he’s not exactly running on economics.

The most virulent Republican critics come from the bottom of the polls. Mike Huckabee, Bobby Jindal and Rick Santorum all publicly opposed TPA and the accompanying trade deal. But among them, only Jindal currently holds office, and as the governor of a Southern state, he’s comfortably positioned to lambast the president without having to stand up to party leadership in the Senate. Even Senator Ted Cruz, who in the past has called Obama a “lawless imperator” and slammed his own party’s leadership for failing to block the Iran nuclear deal, sided with his enemies on fast-track authority. He even penned an op-ed with Representative Paul Ryan in support of TPA. Senator Marco Rubio wrote a similar piece in support of not just the negotiation provision but the entire TPP as well, making Rand Paul the only holdout among the senators running (he was one of five Republicans to vote against TPA).

On the Democratic side, Hillary Clinton was instrumental in advocating for fast track as Obama’s first secretary of state. She has since been accused of flip-flopping on the deal and has yet to give it her full endorsement.

Many unions oppose the deal, giving workers’ advocates like Bernie Sanders common cause with the populist wing of the Republican Party. Clinton’s main rival in the polls, Sanders has called the TPP “job killing” and said “it was drafted with input by special interests and corporate lobbyists but not from the elected representatives of the American people.”