Koster was caught on tape opining about what he called "the rape thing" by Fuse Washington, a liberal organization based in Seattle, and published by Seattle's alternative weekly The Stranger.
In the case of a mother's life being in danger, "I'm not going to make that decision," Koster began by saying, adding that "Incest is so rare, I mean, it's so rare."
"But on the rape thing," he continued, "it's like, how does putting more violence onto a woman's body and taking the life of an innocent child that's the consequence of this crime, how does that make it better? You know what I mean?"
Koster's comments drew criticism from his Democratic opponent Suzan DelBene, whose spokesman said Koster was "out of touch," according to Reuters.
"There are far too many extreme politicians out there that are trying to be involved in a woman's personal medical decisions about her pregnancy," said Sara Kiesler of Planned Parenthood Votes Northwest, the Seattle Post-Intelligencer reported.
Larry Stickney, Koster’s campaign manager, defended his candidate's statements, the Seattle Times reported.
“Consider that John was at a dinner with many people trying to get his attention, yet his words were still thoughtful and heartfelt,” he said. “He very clearly and honestly stated his thoughts on an extremely sensitive subject. He has nothing to be ashamed of here.”
Koster's comments are the latest in a string of controversial remarks on abortion and women's issues from Republican candidates: Missouri Senate candidate Todd Akin has said that women's bodies can prevent pregnancy in instances of "legitimate rape"; Indiana Senate candidate Richard Mourdock said last week that pregnancy from rape was "meant to happen"; and Illinois Representative Joe Walsh argued that a woman's health is "almost never endangered" by pregnancy.
"The decisions should be left to a woman, her family and her faith and not be influenced by a John Koster or a Todd Akin or any politician," Kiesler added.