Liberals are gearing up for a fight with the Obama White House and they’re hoping to enlist Hillary Clinton on their side.

Labor unions and other progressive groups, burned by the North American Free Trade Agreement signed by Bill Clinton, have been hoping to derail the Trans Pacific Partnership, a comprehensive new trade deal being negotiated by the Obama administration with a dozen countries.

CREDO, a San Francisco-based liberal group that has raised tens millions of dollars for progressive groups and has more than 3.5 million members, is calling on Clinton to oppose the deal.

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“We can get a huge boost in our fight to stop this secret trade deal, which is being negotiated behind closed doors by the governments of a dozen countries (including ours) in collusion with corporate interests, if the next leader of the Democratic Party publicly goes on record against Fast Track and the TPP now,” the group will tell its members in a campaign email to go be sent out Thursday morning.

With a fight likely to heat up soon on Capitol Hill over a bill to give Obama authority to “fast track” approval of the deal, trade could be one of the first major policy items Clinton will have to address after she announces her second presidential campaign, which is expected to happen this month.

“What does Secretary Clinton really believe on trade? If she wants to be president, she must commit to us that she stands for and with us,” the CREDO email continues. “If Secretary Clinton wants to become President Clinton, she must come out and oppose Fast Track authority for trade deals like the TPP.”

The group then asks supporters to sign a petition to “Tell Secretary Hillary Clinton: Publicly announce your opposition to Fast Track and the TPP.”

Clinton has not come down either way on TPP, but she seems unlikely to side with the group.

In her 2014 memoir “Hard Choices,” Clinton wrote that she would “reserve judgment” until the deal was finalized. But she continued: “It’s safe to say that the TPP won’t be perfect – no deal negotiated among a dozen countries ever will be – but its high standards, if implemented and enforced, should benefit American businesses and workers.”

Clinton promoted the trade deal while serving as secretary of state and opposing the treaty or “fast track” authority would be a major betrayal of President Obama on one of his top legislative priorities. Clinton will find ways to contrast herself with Obama, but is otherwise expected to hew close to the president on big ticket items.

Trade is one of few issues that deeply divides the Democratic Party today, and could be a place where a primary challenger outflanks Clinton her left.

Sen. Bernie Sanders, a Vermont Independent considering a long-shot run as a Democrat, has already vocally opposed TPP. “The Trans-Pacific Partnership is a disastrous trade agreement designed to protect the interests of the largest multi-national corporations at the expense of workers, consumers, the environment and the foundations of American democracy,” he has said.

Popular support for freeing trade has softened since the first Clinton administration, but a clear majority still support the concept of trade in general. Support for TPP specifically is less clear.