Most of those who reclaimed Republican seats ran hard against free trade, globalization, and any sort of moderate immigration policy. That these Democrats won makes it likely that others will take up their reactionary call. Some of the newcomers may even be foolish enough to try to govern on the basis of their misguided theory.
Greg Mankiw also touches on the subject:
Some of my best friends are Democrats. They often like to think that their party is good for international trade...
Those of you who want to delve into some deep thoughts on free trade might read this essay.