Fiorina is an anti-abortion rights Republican who ran for the Senate in California in 2010 and has since been a major player in helping the NRSC with fundraising. The group stood by Mourdock following his controversial remarks, which caused a media firestorm last week.

"I struggled with it myself a long time but I came to realize that life is a gift from God, that I think even when life begins in that horrible situation of rape that it is something that God intended to happen," Mourdock said during a Tuesday Senate debate with Rep. Joe DonnellyJoseph (Joe) Simon DonnellyDemocrats now attack internet rules they once embraced Dem group launches M ad buy to boost vulnerable senators Senate rejects Trump immigration plan MORE (D-Ind.).

After an initial clarification didn't quash the story, Mourdock said on Wednesday that he was sorry if anyone had misconstrued his remarks, but did not apologize for his intended meaning. Many Republicans, including Fiorina, have since said the comments amounted to a suitable apology.

"The apology — as I said before, roll this tape back — is if anybody misinterpreted what I said," Mourdock said Wednesday. "I spoke from my heart. For speaking from my heart, for speaking from the deepest level of my faith, I cannot apologize."

He and Donnelly had already been locked in a tight race. On Friday he released a post-debate poll showing the two tied, while the Democratic Senatorial Campaign Committee put out a pull that showed Donnelly jumping to a seven-point lead. Republican hopes of winning back the Senate dim considerably if Donnelly beats Mourdock.