Democratic presidential candidate Hillary Rodham Clinton speaks about her renewable energy plan, Monday, July 27, 2015, at the Des Moines Area Rapid Transit Central Station in Des Moines, Iowa. (AP Photo/Charlie Neibergall)DES MOINES, Iowa (AP) — Calling climate change one of the “most urgent threats of our time,” Hillary Rodham Clinton laid out elements of a sweeping plan Monday that would see every U.S. home powered by renewable energy by 2027, even as she declined to take a position on the Keystone XL oil pipeline opposed by environmental activists.