Forty-four senators in the Democratic caucus voted on Tuesday to block action on a crucial "trade promotion authority" bill, delivering an embarrassing setback to President Barack Obama, who strongly supports the bill - and, more importantly, sowing doubts about U.S. leadership among friends and foes around the world. Leaders of both parties swore that this would not be the final word, that they would find a face-saving exit from the arcane procedural conflict that Senate Minority Leader Harry Reid, D-Nev., is using as a fig leaf for the ascendant anti-trade agenda within his party.

As it happens, they are probably right, in part because there are still enough Democrats in the Senate (in addition to the one, Thomas Carper of Delaware, who had the guts to vote against Reid on Tuesday) who favor trade. Still, it's remarkable how much power the anti-trade left wing of the Democratic Party has come to wield within the Senate, which historically was a bastion of bipartisan pro-trade sentiment. Obama wants trade promotion authority — "fast-track" authority — to grease the legislative skids for his proposed Trans-Pacific Partnership, a measure that would enhance U.S. exports to Asia, as well as security ties to key nations such as Japan.Progressives oppose the trade deal on the spurious grounds that it would kill American jobs.

So powerful has the opposition on the left become, in fact, that it has turned the party's presumptive presidential nominee, Hillary Clinton, into a quiet follower on the issue, rather than the forceful leader she once was - and still could be. While her opponents for the Democratic nomination populistically posture, all she has mustered are a couple of anodyne remarks. "Any trade deal has to produce jobs and raise wages and increase prosperity and protect our security," she said in a recent visit to New Hampshire.

Clinton's dash for the tall grass is transparently inconsistent with the position she embraced as Obama's secretary of state. "Our hope is that a TPP agreement with high standards can serve as a benchmark for future agreements - and grow to serve as a platform for broader regional interaction and eventually a free trade area of the Asia-Pacific," she wrote in an October 2011 cover story for Foreign Policy magazine. Indeed, given this well-known record, her avoidance now rather insults the electorate's intelligence.

With the president's agenda embattled in the Senate, this would be a good time for Clinton to abandon her political caution and speak up for what she said so recently were her principles. In refusing to take a stand, Clinton is not only abandoning the president she once served but also missing an opportunity to help define the values of the party she would lead in November 2016.

Will Democrats look backward, in the vain hope of sheltering America from global economic forces? Or will they confidently embrace change and competition? Clinton tells prospective supporters that hers is a campaign to "win the future." Her performance on trade so far implies that it's just about winning the nomination.