The Democratic Party once believed in free trade. The latest issue of Bloomberg Businessweek features an article that highlights a peculiar change in the political landscape.

Disapproval trails Democratic Senator Ron Wyden these days. Over the past few months, he’s become the White House’s chief congressional ally on free trade, helping President Obama, Treasury Secretary Jack Lew, and U.S. Trade Representative Michael Froman push for a bill to streamline the passage of trade deals. That’s alienated liberal activists in Oregon, his home state, who show up at the senator’s public events flying a 30-foot-long blimp that says, “Ron Wyden: It’s up to you. Don’t betray us!”

In the Senate the shadows are cast by members of Wyden’s own caucus: Minority Leader Harry Reid of Nevada, Dick Durbin of Illinois, Chuck Schumer of New York, and Elizabeth Warren of Massachusetts, all of whom oppose giving the president “fast-track” trade-promotion authority, which limits Congress’s ability to modify trade agreements the administration negotiates with foreign governments. “The answer is not only no, but hell no,” Reid said in a Capitol Hill press conference on April 21. His advice to Wyden: “Slow this thing down a little bit.”

Wyden is even up against some key Republicans, including former U.S. Trade Representative Rob Portman, who was once in charge of negotiating such treaties under President George W. Bush. Now a senator from Ohio, he’s teamed up with Schumer to put fast track on a slower track by requiring treaties to include enforceable prohibitions against countries’ suppressing their currencies to gain a competitive advantage. …

… The fast-track bill, which is expected to come to a vote in May, would let Congress instruct negotiators what it wants out of a trade deal, but then stop lawmakers from tacking on any amendments when presented with the treaty for approval. The White House argues that trading partners are reluctant to negotiate with the U.S. in the absence of fast-track authority for fear that complex and hard-won compromises will be unraveled on the floor of the House or Senate, where lawmakers get final say.

If Congress grants Obama fast-track authority, which expired in 2007, the U.S. has a good chance of concluding two big trade-liberalization treaties, one in the Pacific and one in the Atlantic. Without fast track, both deals may fall apart. “I think the gate closes,” says Gary Hufbauer, a senior fellow at the Peterson Institute for International Economics. “I don’t think you’ll go forward with any of these.”

Why is fast-track legislation a good idea? John Hood has some thoughts on the matter.