WASHINGTON — Few issues in this campaign cycle seem as toxic as trade: Both major-party presidential candidates oppose President Obama’s 12-nation Trans-Pacific Partnership, and congressional leaders, having refused all year to vote on the trade accord until after the election, say they will not do so even then — potentially killing the largest regional trade pact in history.

So that must mean voters are overwhelmingly opposed, right? Wrong.

National polls continue to show that Americans either narrowly favor international trade generally, and the so-called T.P.P. specifically, or are split. Younger voters are especially favorable. But Republicans are not, reflecting the influence of the anti-trade nominee Donald J. Trump on his traditionally pro-trade party. And certainly trade remains more unpopular in battleground states like Ohio, where it is blamed for years of manufacturing job losses.

Yet the level of support for trade agreements in general, and the pending Pacific pact in particular, stands in notable contrast to the toxicity of trade in an election season largely defined by anger among working-class voters. What matters to many politicians, however, is the fact that the opponents are the ones most motivated to vote based on the issue — just as they are on issues like immigration and gun restrictions that also have more support than divisive debates suggest.

“There really is a lot of ambivalence on the part of the public” toward expanded foreign trade, said Jay Campbell, a senior vice president with the polling firm Hart Research, who is not working for a presidential campaign.