Sen. John Thune (R-S.D.) speaks  during a news conference on the trade bill on Thursday on Capitol Hill. (Alex Wong/Getty Images)

On Thursday, after a week of wrangling, the massive trade deal with Asia known as the Trans Pacific Partnership took crucial step forward through the Senate. But it’s far from out of the woods in Congress, with an even harder path ahead in the House. And in debating measures that would require an up or down vote on the treaty, with no amendments, one objection keeps coming up: Lawmakers would have to grant the President that concession without being able debate what’s actually in the agreement itself.

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That’s because trade negotiations are carried out largely in secret. A limited number of cleared “stakeholders” from business and public interest groups can see the text, and legislators are allowed to look at it in a sealed room in the basement of the Capitol. But they can’t take notes, and they are not even supposed to talk to anybody about the details; they were only recently allowed to bring personal staff with a security clearance. Trade language is arcane, and politicians aren’t usually wonks -- they need experts to tell them what it means.

Of course, the U.S. trade representative has reasons for keeping the discussions under wraps. Other countries may not put their best proposals on the table, the office has said, if the whole world can see them. But right now, with the perception that America will soon be subject to an international trade pact influenced by corporate interests behind closed doors, whatever level of strategic advantage that’s created among negotiating parties is exacting political costs that might keep the deal from ever making it through Congress at all.

So is all that secrecy really worth the price?

Susan Aaronson, a professor at George Washington University who studies trade policy, says the lid on information has largely proven counterproductive. First of all, it’s hard to back up the claim that secrecy achieves better outcomes in bargaining.

“If they were to use game theoretic models to talk about it, there’s no evidence that you lose negotiating clout if you’re transparent,” Aaronson says. (A quick scan of economic research databases doesn’t appear to turn up any conclusive evidence either way.) “I just really don’t understand the logic. I think the only logic is that this is how it’s always been done.”

Meanwhile, she says, keeping things out of public view has undermined support for a deal that is not likely to happen without public trust. While Americans tend to support free trade in principle, it’s become more and more clear that the Trans-Pacific Partnership is about much more than lowering tariffs -- it requires countries to change their domestic regulations in order to harmonize investment rules across borders. Plus, the legacy of the agreement between Canada, Mexico and the United States known as NAFTA has left a bad taste in many mouths, requiring the White House to prove that this trade agreement is different.

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But it can’t prove that. Even if U.S. Trade Ambassador Michael Froman thinks that opponents of the TPP are being disingenuous in their claims about how it could affect local health and safety regulations, for example, he can’t put the text out in public to prove anybody wrong. Instead, draft chapters have seeped out via Wikileaks, leading to outrage when people find out what’s in them -- and fear that the rest of the agreement might be just as bad.

“This is saying, 'We need to build trust among the negotiating parties, and that trust is more important than the trust among the public at whom the policy is aimed,’” Aaronson says. “The more information you put out, you empower people with the facts, but you also disabuse them of the demagoguery related to the facts.”

Aaronson says that it makes sense for some elements of the negotiations to remain out of public view, such as confidential business information. But there are ways to open other things up, which some organizations are already doing. The World Intellectual Property Organization, for example, has published draft texts and has even Webcast negotiations. The European Commission is posting the text of its proposals online for the Transatlantic Trade and Investment Partnership negotiations.

Even Robert Zoellick, who served as U.S. trade representative from 2001 to 2005, expressed surprise that the negotiating texts were not made more generally available. “I’m actually a big believer in the transparency of those arrangements, so I don’t know why they’ve been more restrictive,” he said at a speech at the Wilson Center in 2013.

With the TPP, the United States isn't alone in its secrecy. Japan hasn't even allowed its legislators to see the text, to their chagrin. And public interest advocates in other countries, such as Australia and Canada, are impatient with their own governments' tight lips.

Even if trade negotiations have traditionally enjoyed some degree of privacy, Aaronson says, times have changed. The public expects new levels of access to information -- which the Obama administration has granted in so many other areas of government -- and gets suspicious when requests are denied.

“That’s the problem. In the age of the Internet, it’s just not working,” Aaronson says. “It seems to me that the Internet has truly changed the way we govern. Why should we presume that it will not change how trade negotiations work?”

Correction: A previous version said that members weren't allowed to bring staff to view the TPP texts. They have been allowed to bring committee staff, and were recently allowed to bring personal staff with appropriate clearances.