Republican Sen. Susan Collins said she does not believe Justice Brett Kavanaugh sexually assaulted Dr. Christine Blasey Ford but does believe Ford was assaulted by someone."I do not believe that Brett Kavanaugh was her assailant," Collins told CNN's Dana Bash. "I do believe that she was assaulted. I don't know by whom. I'm not certain when."The Maine senator said she weighed her decision on the FBI report released to senators last week. The report did not include interviews with Ford or Kavanaugh.Collins said she found the accuser's allegation of sexual assault "sincere, painful and compelling" but the FBI found no corroborating evidence. She said it's when "passions are most inflamed that fairness is most in jeopardy.""I found Dr. Ford's testimony to be heart-wrenching, painful, compelling, and I believe that she believes what she testified to," Collins said. "But we also had a case where Judge Kavanaugh came forward and said, 'I'm 100 percent certain that this did not happen,' so here you have two people who are each 100 percent certain of what they're saying under pain of perjury. So then I had to look at the other evidence, and was there corroborating evidence, and that's why I pushed hard for the FBI to do a supplemental background investigation."Collins did not announce her vote until Friday. She was a crucial vote for Republicans who have a thin majority in the Senate.Kavanaugh was confirmed Saturday with a vote of 50-48.Collins was cheered by Republicans. Former President George H.W. Bush praised her for "political courage and class."The Associated Press contributed to this article.