ATLANTA — On a sweltering morning in July, Sonny Perdue, the newly minted secretary of agriculture, strode across the stage of a convention hall here packed with 7,000 members of the School Nutrition Association, who had gathered for their annual conference.
Mr. Perdue then outlined how his department was loosening some of those rules. Some in the audience cheered. Some walked out. School food was not going to escape the sharp political divisions that began to simmer in the Obama years and have been laid bare by the election of President Trump