But the issue injected itself into the debate with fresh force this week with an amendment from House Ways and Means Committee Chairman Paul Ryan that would block the president from using trade negotiations as an avenue to write future climate deals.
The amendment—which comes on a customs bill that would amend the trade bill—was meant to appease Republican concerns that President Obama would use his negotiating authority to act on climate, but it enraged the Left and appears to be one of the factors that pushed Pelosi over the edge.
She singled out the amendment, playing it against language she wrote 25 years ago on the International Development and Finance Act, which required the World Bank and other multilateral development banks to hold environmental reviews of projects they were funding.
"The connection between the environment and commerce is inseparable," she said.
To be sure, there are plenty of interests pushing to defeat the fast-track bill. In her speech, Pelosi cited protection of American employment and security concerns as well, and labor voices have been among the strongest in opposition to the bill. Many Democratic opponents said they were most concerned about the impact a fast-track bill would have on jobs in their district.
The White House has pushed back against the environmental concerns, with the administration telling supporters that a trade deal can actually strengthen environmental protections. Rep. Steve Israel said that President Obama even talked about climate change when he met with Democrats Friday morning to lobby for the bill. But, he added, "I don't believe that one issue swayed votes."
Pelosi's highlighting of the climate language, however, signaled how strong the environmental opposition has played in the trade debate. Even though the White House has increasingly tied climate change to a variety of issues, it generally doesn't make a splash in Congress' debates over economic policy.
But for opponents of fast-track, anything goes.
Rep. Earl Blumenauer, for instance, a lawmaker widely considered to be a progressive champion, was one of only two Democrats to support fast-track when it was approved by the Ways and Means Committee. That vote earned Blumenauer jeers from environmentalists, including Friends of the Earth, a progressive environmental group that went after the congressman in an ad casting his vote as a betrayal of the environment with devastating consequences for the climate.
Facing attack from his own allies, Blumenauer has called for a slate of environmental protections to be built into the trade push, including measures aimed at holding corporations accountable for violating environmental laws.
"Today's move to delay final decision on the trade package represents a significant victory in the fight to ensure that toxic trade agreements like the [Trans-Pacific Partnership] do not get bulldozed through Congress," said Friends of the Earth president Erich Pica. "The political deals that President Obama cut with Republicans to slash Medicare funding and undermine action on climate change revealed how low Obama is willing to go in selling out ordinary Americans and the environment."