FLOURTOWN, Pa.  The primary race between Senators Hillary Rodham Clinton and Barack Obama could be decided in places like this bedroom community in southeastern Pennsylvania, where polls show the two Democratic presidential candidates running tight.

So it was with obvious gravity that 74 fourth graders at Erdenheim Elementary School assembled this week behind the glass and tan brick walls of their classrooms to debate the campaign’s central issues. The children, most 9 or 10, then signaled their preferences for the Democratic nomination in a gradewide straw poll.

“It’s a battle between man and the environment, and the environment’s losing right now,” Michael Kassabian announced to his fellow voters in Renea Boles’s room, before explaining that he was endorsing Mr. Obama at least partly because of the candidate’s enthusiasm for renewable energy sources.

Henry Centeno said that the candidates’ stances on health care should take precedence, and that his support depended on which candidate would guarantee health insurance for anyone age 25 or younger. Why 25? “If it’s 25,” he said, “Miss Boles would still have free health care.” (His teacher, he knew, is 24.)