U.S. Republican presidential candidate Marco Rubio speaks at the Family Leadership Summit in Ames(This Aug 9 story changes paragraphs 1, 3 and 4 to clarify that while life-of-mother exception not cited in debate, Rubio did sponsor a Senate bill that included such an exception) By Megan Cassella WASHINGTON (Reuters) – Florida Senator Marco Rubio on Sunday defended his stance against abortion without exceptions for rape or incest that he was asked about during a debate among Republican presidential candidates on Thursday.