Leving's piece in the Washington Post is by no means an embarrassment to progressives or the Democratic Party.  His opposition boils down to this statement about labor standards:

"Regrettably, CAFTA sanctions the status quo or worse by saying to these countries: "Enforce your own laws" when it comes to internationally recognized labor standards."

Trade in itself is not a bad thing, but trade agreements clearly haven't lifted up Latin America out of poverty.  Go to Mexico, go to Brazil, and go to El Salvador and see for yourselves.  Levin and Senator John Kerry are right to say that we need agreements with stronger labor provisions.  "Trade" isn't everything, and for many in Central American, it in itself isn't much of anything. 

One of the most successful trade treaties occured with Cambodia b/c of its rewards for protections of worker's rights.  The country has held its own against China even after an end to textile quotas, largely b/c of these measures.  If we followed this path in El Salvador, Guatemala, Honduras, and the Dominican Republic, they might end up with the same results.  Special interest-driven treaties like CAFTA will just lock-in the status quo.