Clinton, accompanied by Sen. Evan Bayh, D-Ind., addressed about 400 employees at Allison Transmission in Indianapolis, The Indianapolis Star reported. The New York senator also promised "a new generation" of defense manufacturing jobs if she becomes president.

Obama, at a San Francisco fundraiser, suggested many U.S. voters in small towns are bitter because of lost jobs and economic decline. The Illinois senator said those people "cling to their guns or their religion or their antipathy to people who are not like them."

"I grew up in a church-going family, a family that believed in the importance of living out and expressing our faith," Clinton said. "The people of faith I know don't 'cling' to religion because they are bitter. People embrace faith not because they are materially poor, but because they are spiritually rich."