WASHINGTON — (CNN) Rick Santorum, who is a strong proponent of defunding Planned Parenthood, made a dig Friday directed at fellow GOP presidential candidate Ben Carson for his past use of fetal tissue for medical research, calling it “morally suspect.”

Santorum told CNN’s “New Day” that when a campaign gets underway and you “see some of these cracks, I think it may show whether the person is really someone who’s going to take on an issue and be strong on it when they get into the very difficult position of being President of the United States.”

When host Chris Cuomo asked the former Pennsylvania Senator if he would participate in fetal tissue research, Santorum said, “No, I wouldn’t,” adding that a lot of women are told “if you get an abortion good things can come from it, we’re going to use this tissue for a lot of reasons.”

Santorum said that fetal tissue research is sometimes used “to make women feel more comfortable about having abortions.”

Carson, a retired neurosurgeon, defended his research on aborted fetuses Thursday and said that the research does not conflict with his call to defund Planned Parenthood. In the case in question, Carson was co-author of a 1992 study that used tissue from two fetuses.

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