DES MOINES — Emerging on the campaign trail in Iowa after largely shunning the state, Mitt Romney was confronted on Thursday by hecklers on corporate tax policy and told one of them, “Corporations are people, my friend.”

Mr. Romney was speaking at the Iowa State Fair’s soapbox on Thursday morning, but when it was time for the question-and-answer session, the mood turned heated, with a small group of angry hecklers calling on Mr. Romney to support raising taxes on the wealthy to help finance social entitlement programs.

“We have to make sure that the promises we make in Social Security, Medicare and Medicaid are promises we can keep, and there are various ways of doing that,” Mr. Romney said. “One is, we can raise taxes on people.”

“Corporations!” the protesters shouted, suggesting that Mr. Romney, as president, should raise taxes on large businesses.