Mourdock made the comments when asked during a debate Tuesday night whether abortion should be allowed in cases of rape or incest.
He replied: "Even when life begins in that horrible situation of rape, that it is something that God intended to happen."
Mourdock's comments come two months after Missouri GOP Senate candidate Rep. Todd Akin said women's bodies have ways of preventing pregnancy in cases of what he called "legitimate rape."
Mourdock is locked in a tight race with Democrat Rep. Joe Donnelly. Democrats quickly criticized Mourdock's comments, and a spokeswoman for Mitt Romney says the GOP presidential hopeful disagrees with Mourdock.