This article on various Democrats using free trade's toll as a cudgel against their Republican opponents is an interesting one. In the abstract at least, free trade enjoys broad support. In the abstract. But trade, like abortion or taxes, is a voting issue. While "fair trade" isn't the most broadly agreed upon policy -- unlike the minimum wage or Canadian drug reimportation -- for the fraction of voters affected or unnerved by globalization, it moves them to the polls.
In recent elections, Democrats have tended to emphasize the issues with the broadest constituencies, not the most intense ones. So they've ended up touting policies the electorate agrees with and does not vote on -- after all, if the electorate agreed and did vote on that issue, the GOP would rapidly notice its wisdom and make it a central policy plank. So while this strategy garnered very high numbers of Americans telling pollsters they agreed with the Democratic position, it didn't lead to all that many voting for the Democrat.
Strategies built on smaller, more intensely supported policies have been more successful, at least to judge from the Republican Party's recent history. And many of these issue are asymmetrically intense -- someone in agreement will vote for you because of your support, but someone in disagreement will not vote against you because of that issue. My guess is trade is one of those issues, where those affected will make it a first-order priority, while the rest may vaguely believe in free trade, but won't particularly allow it to influence their vote. And if that's right, you may see a lot of Democrats mounting stronger-than-expected challenges in the Rust Belt.
