When former President Donald J. Trump met with House Republicans last month, he touched on a mix of policies core to his economic agenda: cutting income taxes while also significantly raising tariffs on foreign goods. Mr. Trump told Republicans he would “love to raise tariffs” and cut income taxes on Americans, potentially to zero, said Representative Marjorie Taylor Greene, Republican of Georgia. “Everyone was clapping in the room,” Ms. Greene said. “He said, ‘If you guys are going to go...