President Donald Trump's tariffs imposed on key trading partners will put some Republicans in tough spots this year.

Thirty-one percent of registered voters say they are very uncomfortable with backing a candidate who supports tariffs on countries such as Canada, Germany and China, according to an NBC News/Wall Street Journal poll released Thursday. Twenty percent said they would have reservations about voting for someone who backs the measures.

Only 10 percent say they are enthusiastic about voting for someone who supports tariffs, while 17 percent responded that they are comfortable with a pro-tariff candidate.

Trump's push to put duties on imported products has left many GOP candidates with difficult decisions. Some Republicans who supported free trade in the past have backed Trump's protectionist moves in order to better align with the president and the voters who support him.

The president won the White House partly through pledges to crack down on alleged trade abuses by foreign countries that he says sapped American jobs.

He took his most divisive trade action last week when he decided not to exempt allies Canada, Mexico and the European Union from tariffs of 25 percent and 10 percent on steel and aluminum exports, respectively. The move has sparked retaliatory tariffs and backlash from a bipartisan group of senators who introduced a bill to curb Trump's tariff powers on Wednesday.

While most voters overall may disapprove of tariffs, Americans in key states or House districts with heavy manufacturing presences often hold positive views of the duties. Trump's trade rhetoric helped him to win such states as Ohio and Michigan in 2016.

Trump's trade policy has taken a role in numerous races such as the campaign for a Senate seat in Ohio. Incumbent Democratic Sen. Sherrod Brown has long criticized free trade agreements. But Rep. Jim Renacci, a Republican who previously supported free trade, has changed his tune this year as he tries to defeat Brown.

Trump's moves have also factored into key races in Midwestern states such as Iowa, where the president's threatened tariffs on Chinese products prompted Beijing to propose putting duties on soybeans and other agricultural products.

The poll also found that 45 percent of registered voters say they are less likely to support a candidate who backs Rep. Nancy Pelosi for House speaker should her party win a House majority in November.

The NBC/Wall Street Journal poll surveyed 900 registered voters from June 1 to June 4 and has a margin of error of plus-or-minus 3.3 percentage points.