Protection and free trade

There has been some debate on whether the "trade war" that seems to be emerging will help or hurt Donald Trump.  Catherine Rampell says that protectionists are a "tiny minority" and that "even before Trump ran for office, Democratic voters were more positive on trade than the politicians in their own party."  I think that the second part is wrong, and I will probably have a post on that soon, but today I'll focus on the first part.  I have had several posts that say that protectionism is a popular position--that a lot of people see trade as basically a competition, rather than mutually beneficial.  I looked for additional questions on this topic, and found one that was first asked in 1988: "Which of the following statements comes closer to your opinion?...Trade restrictions are necessary to protect domestic industries. Free trade must be allowed, even if domestic industries are hurt by foreign competition."  The percent favoring restrictions minus the percent favoring free trade:

The mention of "even if domestic industries are hurt" probably pushes responses in favor of the first option, but the striking thing is that sentiment seems to be moving in that direction--more educated people are generally more supportive of free trade, so rising educational levels should produce a movement away from restrictions.  The changes do not seem to be closely related to economic conditions--the strongest support for restrictions (68% to 24%) came in March 2008, when the 2008-9 recession was just beginning and was pretty mild.  There was actually a move towards support for free trade between 2008 and April 2009.

[Data from the Roper Center for Public Opinion Research]