President Trump's tariffs are introducing a new, wildly unpredictable issue into the midterm elections, thanks to their heavy impact on states with critical Senate races as well as their likely role in House races across the country.

Expand chart Data: U.S. Chamber of Commerce. Note: Dollar amounts reference total value of goods in 2017. Cartogram: Lazaro Gamio/Axios

Why it matters: This puts GOP candidates in a weird position: Speaking out against trade policy that's hurting their state or district could turn off voters who would view that as criticizing Trump. But Democrats aren't exactly free traders, and they're not piling on the president's tariffs the way they attack his other policies.

The big picture: Politically speaking, "If the Chinese blink and back down, it's a victory for Trump and a plus for Republicans," said Chris Wilson, a GOP pollster who worked on Sen. Ted Cruz's 2016 campaign. "But the risk if we get into a prolonged trade war is there will be local and potentially national impacts."

What they're saying: Republican Senate candidates trying to defeat Democrats in red states that Trump won aren't going to jump at the opportunity to undermine their support of the president, despite the party's traditional free-trade ideology.

In North Dakota — one of the GOP's best pickup opportunities this cycle — Rep. Kevin Cramer has issued carefully worded statements on Trump's tariffs, emphasizing the need to protect farmers while stopping short of criticizing the president. He also accused Democrats of stoking "hysteria" over the tariffs.

— one of the GOP's best pickup opportunities this cycle — Rep. Kevin Cramer has issued carefully worded statements on Trump's tariffs, emphasizing the need to protect farmers while stopping short of criticizing the president. He also accused Democrats of stoking "hysteria" over the tariffs. Sen. Heidi Heitkamp, the Democrat who holds the seat now, has said the tariffs would cause a "devastating blow" to the state's agriculture sector and accused Cramer of belittling his constituents.

the Democrat who holds the seat now, has said the tariffs would cause a "devastating blow" to the state's agriculture sector and accused Cramer of belittling his constituents. A similar dynamic has played out in the race for Tennessee's open Senate seat, where Republican Rep. Marsha Blackburn has called the tariffs "part of a negotiation and a process," while former Democratic Gov. Phil Bredesen has criticized the tariffs in a TV ad.

The other side: Democrats, however, aren't all universally opposed to the tariffs. Some have always been skeptical of free trade and support the tariffs, while others say they wish Trump had executed them better.

Sen. Chris Van Hollen, the caucus's campaign chair, said each member will act based on how their state is impacted. "The bottom line here is each member’s job is to defend the interests of the people in their states," he said.

the caucus's campaign chair, said each member will act based on how their state is impacted. "The bottom line here is each member’s job is to defend the interests of the people in their states," he said. "I support the president’s tariffs. I wish that they would be done better," said Sen. Sherrod Brown of Ohio, who said he's been concerned about trade policy long before Trump became president.

I wish that they would be done better," said Sen. Sherrod Brown of Ohio, who said he's been concerned about trade policy long before Trump became president. Others are more skeptical. “It’s already taking us down a road that’s going to have some real negative impact, particularly on agriculture and construction," said Sen. John Tester of Montana. "If I thought there was an end game here that he could actually achieve, I’d be a little less concerned."

“It’s already taking us down a road that’s going to have some real negative impact, particularly on agriculture and construction," said Sen. John Tester of Montana. "If I thought there was an end game here that he could actually achieve, I’d be a little less concerned." "I do think we need to be aggressive with China, but do it in a manner that’s strategic and not in a way that’s impulsive or lacking in a calculated outcome to help our workers and our economy," said Sen. Bob Casey of Pennsylvania. "Sometimes I don’t know if the president’s able to do that.”

It's not just Senate races that could be affected by the tariffs. One GOP operative said that in House seats in the Midwest, where the tariffs are starting to hit soybeans and dairy farmers, "it could be a real issue."