Republican White House hopeful Mitt Romney, a Mormon facing doubts about his conservative credentials, said Saturday he had the endorsement of five former US ambassadors to the Vatican. Romney's campaign unveiled a letter from the ex-envoys hours before a debate in which he was to face off against his rivals, including Catholics Rick Santorum and Newt Gingrich, who have cast him as a weak-kneed moderate. The former ambassadors said they were "united" behind Romney "because of his commitment to and support of the values that we feel are critical in a national leader" and "experience, vision and commitment to the...