On Wednesday, the day after President Obama’s State of the Union address, a handful of Democratic House members, along with one senator, Bernie Sanders of Vermont, held a news conference to denounce one of the very few proposals the president put forward that actually has a chance of passage. The objects of their displeasure were the new trade agreements currently being negotiated by the administration.

“Since I’ve been in Congress, I’ve never seen a trade bill that in any way benefited U.S. manufacturers and workers,” said Representative Louise Slaughter, who has represented the Rochester area for 28 years. She pointed to Kodak as an example of a company harmed by trade accords, especially the landmark North American Free Trade Agreement, or Nafta. Since the deal between the U.S., Canada and Mexico went into effect in 1994, Kodak’s Rochester work force has shrunk to 2,300 from 39,300.

“We are fighting for the future of middle-class families,” said Representative Rosa DeLauro of Connecticut. “These trade deals make it much easier for corporations to send American jobs overseas.” Over the past 20 years, Connecticut has lost more than 96,000 manufacturing jobs, she said, because of agreements that failed to protect American workers.

Sanders told the assembled media that while he liked the president’s speech, “he was wrong on one major issue, and that is the Trans-Pacific Partnership.” He added, “I do not believe that continuing a set of bad policies, policies that have failed, makes any sense at all.”The Trans-Pacific Partnership is a trade agreement currently being negotiated between 12 countries, including Japan, Canada, Vietnam, Mexico, Australia and Peru; the countries involved in the negotiations represent nearly 40 percent of global gross domestic product. It is as complex as it is ambitious.

Yet, while the Republican leadership has vowed to work with President Obama on the Trans-Pacific Partnership (as well as on another deal being negotiated with the European Union), the Democrats have been vocal in their opposition. In the short term, they don’t want to give the president so-called fast-track authority, which would allow the administration to negotiate the deal and then hand Congress a finalized agreement that it could only vote up or down, with no amendments. (Fast-track procedures have been used to conclude 14 trade agreements since 1974.)

You’d need a heart of stone not to be sympathetic to the concerns of the Democrats. Over the last two decades, lots of manufacturing jobs have vanished in the United States, inflicting a great deal of pain on workers. During those same 20 years, Nafta has been in force. Linking those job losses to the existence of Nafta is a leap the Democrats . and progressives in general . have made.

The question that needs to be asked, however, is whether that link is justified. “I am skeptical of definitive judgments on Nafta,” said Edward Alden, a senior fellow at the Council on Foreign Relations. “We started offshoring television assembly in the 1960s” . decades before Nafta. Yes, many assembly plants have been built in Mexico since Nafta went into effect. But China, where millions more manufacturing jobs have migrated . and with which we have a huge trade deficit . doesn’t even have a trade agreement with the United States.

Edward Gresser, the executive director of Progressive Economy, a left-leaning think tank, noted that other factors were taking place at the same time as Nafta: the growth of container ships, the lowering cost of communications, the rise of global industries. With or without trade deals, globalization is an unstoppable force. What Nafta really is, Gresser told me, is a proxy for globalization.

One mistake the Nafta negotiators made more than two decades ago was taking worker rights and environmental protections out of the agreement itself and putting them into a side letter. They were never effectively enforced. Those negotiating the Trans-Pacific Partnership expect to rectify that error this go-round. They are also aiming to pry open the Japanese auto and agricultural markets to American producers, and include protections for a free and open Internet. It has, in other words, a lot more potential to do good than harm.

When I spoke to Slaughter on Thursday afternoon, she was still riled up. “These crazy trade agreements,” she called them at one point. She added, “Rochester really suffered.”

She told me about all the jobs lost at Kodak. “I think Nafta brought down Kodak,” she said. But of course it didn’t. Kodak’s problems came about because digital photography made film unnecessary and Kodak didn’t shift course in time. She was blaming Nafta for Kodak’s self-inflicted wounds.

But then her tone brightened. She told me about all the new companies . 55 in all, she said . that had taken space in the old Kodak buildings. Some were even run by former Kodak engineers.

Which, of course, is precisely the way globalization is supposed to work.