WASHINGTON — Academic researchers claim to have found a link between the adverse impact of trade and the rise of “ideologically strident” politicians like Donald Trump and Bernie Sanders, whose antitrade rhetoric has helped define this year’s presidential race, according to a new study.

Globalization has long had a negative impact on U.S. manufacturing, leading to significant job losses over the past two decades, which has fueled antitrade sentiments in past elections. But this year’s presidential election has seen a more intensely negative debate about the effects of trade on U.S. jobs and led to all but one of the presidential candidates from both parties to stake out positions opposing trade deals and commerce with China.

Now four academics have traced that impact of globalization to the polarization in politics over trade, which they claim has led to the election of more extreme candidates in both parties, according to the paper.

“By favoring those at the extremes of their respective parties, and in particular of conservative Republicans, greater trade exposure does not help candidates to win lopsided electoral victories, but rather abets the electoral ascendance of more ideologically strident politicians,” they argued.

The researchers, who analyzed outcomes in congressional elections between 2002 and 2010, said in the paper they found “strong evidence that congressional districts exposed to larger increases in import competition disproportionately removed moderate representatives from office in the 2000s.”

“Our paper provides the first evidence that connects adverse trade shocks to political polarization,” the four academics said. The authors of the paper included David Autor, a professor in the Department of Economics at the Massachusetts Institute of Technology; David Dorn of the University of Zurich; Gordon Hanson, an economics professor at the University of California San Diego, and Kaveh Majlesi of Lund University in Sweden.

“As an indication of the prominence of globalization in U.S. political debates, presidential candidates from both major parties have agreed on the need to take a much more aggressive line on international trade,” the paper said. “On the right, Republican candidate Donald Trump pledged to impose a 45 percent tariff on U.S. imports from China; on the left, Democratic hopeful Bernie Sanders categorically rejected supporting any trade deal, including the Trans-Pacific Partnership, which had been negotiated by a Democratic president.”

Real estate mogul Trump has bashed China on the campaign trail, accusing the country of manipulating its currency and unfairly hurting U.S. manufacturers.

On the Democratic said, pundits have long claimed that Sanders’ entrenched anti-trade stance is the catalyst behind pushing front-runner Hillary Clinton to the left on trade and shaped her opposition to a trade deal, TPP, that she once helped support as Secretary of State under President Obama.

The researchers studied whether the exposure of labor markets to increased foreign competition has “exacerbated the partisan divisions on Capitol Hill.”

They estimated the impact of imports from China in particular on Congressional elections between 2002 and 2010 to determine whether “adverse economic shocks” from international trade cause lawmakers or voters to support more polarized and extreme views on trade.

Three mechanisms were analyzed in the paper to determine trade shocks affecting regional political divisions.

First, the academics looked at the “anti-incumbent” effect, which generally is based on the hypothesis that economic downturns “are bad for sitting politicians and their parties.”

“We verify in our data that adverse trade shocks diminish vote shares for the party initially in power,” they said. “However, such patterns cannot explain greater partisanship, as on their own they imply that regions suffering a persistent trade-induced decline in manufacturing would simply alternate their support for political parties or churn through elected legislators.”

The second mechanism under review was something called a “realignment effect” that is based on research showing that people who perceive actual or expected declines in economic opportunity often shift their political preferences.

While the researchers cited a study that found evidence between 1998 and 2010 that U.S. counties exposed to greater import competition had larger increases in vote shares for Democratic candidates, their findings did not support such a conclusion.

“In our data, we do not find that adverse trade shocks induce a realignment in vote shares toward either major political party,” the paper said.

But they did find “strong support” in a third mechanism known as a “polarization effect, in which a negative economic shock increases the electoral success of both non-centrist left-wing and right-wing politicians.”

“In the 2016 U.S. presidential campaign, candidates from the extremes of both parties have singled out China as a principle cause for U.S. economic malaise. China bashing is now a popular pastime as much among liberal Democrats as among Tea Party Republicans,” they concluded. “Our contribution in this paper is to show that this political showmanship is indicative of deeper truths. Growing import competition from China has contributed to the disappearance of moderate legislators in Congress, a shift in congressional voting toward ideological extremes, and net gains in the number of conservative Republican representatives, including those affiliated with the Tea Party movement.”