On Wednesday morning, President Trump took a call from Brooke Rollins, his secretary of agriculture, who relayed a growing sense of alarm from the heartland.

Farmers and agriculture groups, she said, were increasingly uneasy about his immigration crackdown. Federal agents had begun to aggressively target work sites in recent weeks, with the goal of sharply bolstering the number of arrests and deportations of undocumented immigrants.

Farmers rely on immigrants to work long hours, Ms. Rollins said. She told the president that farm groups had been warning her that their employees would stop showing up to work out of fear, potentially crippling the agricultural industry.

She wasn’t the first person to try to get this message through to the president, nor was it the first time she had spoken to him about it. But the president was persuaded.

The next morning, he posted a message on his social media platform, Truth Social, that took an uncharacteristically softer tone toward the very immigrants he has spent much of his political career demonizing. Immigrants in the farming and hospitality industries are “very good, long time workers,” he said. “Changes are coming.”

Some influential Trump donors who learned about the post began reaching out to people in the White House, urging Mr. Trump to include the restaurant sector in any directive to spare undocumented workers from enforcement.