Energy affordability dominated the debates, but the candidates disagreed about the causes and how to solve the crisis.By Nathaniel EisenOver the course of two weeks in October, Maine’s incumbent Republican Sen. Susan Collins and her Democrat challenger, former state Senate President Troy Jackson, met for four debates. Each debate focused heavily on energy affordability, and each exchange followed roughly the same script: When Jackson brought up the high costs of heating a home with oil, Collins volleyed back by talking about the high costs of powering it with electricity, and vice versa.