Angry anti-trade rhetoric is flying from political podiums on the left and the right this year, but it's not at all clear that Americans broadly agree with their politicians.
But Americans of both political parties are inconsistent on trade. At any given time, as much as 10 to 30 percent of respondents have no opinion about open trade, regardless of their party affiliation, and those voters can swing one way or the other in response to politicians.
In March, 52 percent of Republicans told Pew that they thought trade agreements were generally a good thing for the country, while 39 percent said they were bad. That's almost a complete reversal from the same poll in May 2015. Democrats, meanwhile, moved in the opposite direction over the same time period.
Democratic nominee Hillary Clinton has backed away from free trade deals like NAFTA and President Barack Obama's Trans-Pacific Partnership, but Republican nominee Donald Trump seems to have tapped into America's ambivalence on free trade by pushing two seemingly contradictory ideas.
On the one hand, trade protectionism at least appears to be part of Trump's plans — in the speech announcing his candidacy, he said he would protect American auto jobs by imposing a 35 percent tax on parts coming over the Mexican border. He repeated that idea in a CNBC interview on Thursday.
"You can't just leave the United States and there's no consequence," he said. "Every time they ship in a unit, they're going to have to pay something."
On the other hand, Trump has repeatedly said he is "all for free trade," a position that is in keeping with the traditional Republican platform.
"I am not an isolationist," Trump told CNBC on Thursday. "I'm a free-trader. I want free-trade but it's got to be fair trade, it's got to be good deals for the United States."
A Trump spokesperson declined to clarify how a policy could be both pro-tariff and pro-free-trade, which is by definition trade without tariffs or other barriers. But that incongruous position seems to have struck a chord with Trump supporters, many of whom have been on the losing side of trade globalization.
A decade ago, not only did Republicans tend to support free trade, but they supported it more than Democrats, who often sided with trade unions against the deals.
Both sides became more skeptical of trade deals between 2007 and 2011, but since that period the parties have switched sides on the issue, according to the Pew data.
It's unlikely that the reversal between the two parties is a fluke in the Pew data — a similar trend shows up in another long-time poll question posed by Gallup: "Do you see foreign trade more as an opportunity for economic growth through increased U.S. exports or a threat to the economy from foreign imports?"
In Gallup's data, Republicans were fans of foreign trade during the first half of George W. Bush's presidency, but less so in the second half and under Obama. The two parties switched after 2011, but at least half of both sides have remained enthusiastic about trade.
Part of the cross-over between the parties may simply be support for the party in power. The administration at any given time is responsible for negotiating individual trade deals, so it's natural for the other party to react in the opposite direction.
Economists tend to be consistent on the issue, however, with the vast majority supporting free trade policies. But it's only recently that regular Americans have warmed up to the idea.
One of the longest data sets available to track American attitudes about free trade is a survey by the Chicago Council on Global Affairs. It asked people if they sympathize with cutting tariffs or think they are necessary (1978 to 1998) and whether they favor agreements to cut trade barriers (2004 to 2014).
When the council asked whether Americans think "globalization" is a good or bad thing, it found a similar pattern to the Pew and Gallup surveys. The "tariffs" and "trade barrier" surveys, however, found that Democrats were consistently more enthusiastic about more open trade policies.
Now is not the first time that U.S. leaders seem to be pushing a trade message that differs from public opinion. The survey data also show that in the '70s, '80s and '90s, while most Americans were pro-tariffs, leaders in both parties and across government agencies, think tanks and other organizations supported cutting tariffs, with Republicans leading the push.
While Trump's free-trade comments may be the most idiosyncratic, he's not the only candidate to put the issue into the crosshairs. Former Democratic candidate Bernie Sanders said that there's never been a single trade deal the U.S. has negotiated that he's been comfortable with.
Democratic nominee Hillary Clinton has backed away from NAFTA, which she publicly supported as first lady when it was signed by President Bill Clinton. She's also questioned Obama's Trans-Pacific Partnership after once calling it the "gold standard" of trade deals.