As President Donald Trump continues to pursue an escalating trade war with China, it’s unclear whether he fully understands what the consequences might be for Americans, particularly U.S. farmers.

Now, it appears the Senate’s longest-serving Republican — and the third in line for the presidency — doubts whether the concepts can even be explained in terms Trump can understand.

According to The Washington Post, Sen. Chuck Grassley (R-IA), chair of the Senate Finance Committee, plans to write Trump a letter to explain just how much the tariffs will hurt farmers, an argument he has made repeatedly. That’s because he doesn’t think his face-to-face explanations have registered with the president.

“I’m not sure if you talk to him face-to-face he hears everything you say,” Grassley said Tuesday.

Many Republicans object to Trump’s use of tariffs, recognizing that the consequences could cause them to lose political support in their agriculture-heavy states. Grassley said Monday that Congress has allowed the White House to assume too much power when it comes to trade, but he doesn’t see a path to reversing that. That could be because any attempt to challenge Trump will backfire if Trump doesn’t understand what’s at stake.

Axios reported Tuesday morning that according to several current and former officials in the administration, Trump believes China will somehow pay the tariffs. In reality, it will be American companies who have to pay to import goods manufactured in China, and the costs will be passed onto American consumers. But one former aide said it would be fruitless to try to convince Trump of this, because his belief in tariffs is “like theology.”

Trump appeared to confirm this in a pair of tweets Tuesday morning, assuring farmers that they will be bailed out by “massive Tariffs being paid to the United States” — as if those tariffs won’t be paid by entities in the United States.

….This money will come from the massive Tariffs being paid to the United States for allowing China, and others, to do business with us. The Farmers have been “forgotten” for many years. Their time is now!

— Donald J. Trump () May 14, 2019

“Our great Patriot Farmers will be one of the biggest beneficiaries of what is happening now,” Trump wrote. “Hopefully China will do us the honor of continuing to buy our great farm product, the best, but if not your Country will be making up the difference based on a very high China buy. This money will come from the massive Tariffs being paid to the United States for allowing China, and others, to do business with us.”

He added, “The Farmers have been ‘forgotten’ for many years. Their time is now!”

Speaking with reporters Tuesday morning, Trump doubled down.

“So you have no tariffs to pay whatsoever if you’re a business. All you have to do is build or make your product in the United States,” he said. “There is no tariff whatsoever. That really works out very well.”

This article has been updated to include Trump’s latest comments on the impact of tariffs on American companies.