WASHINGTON (AP) - Senate Republicans are making it clear that they won't back down from their vow to block Susan Rice's nomination, if the U.N. ambassador is chosen to succeed Hillary Rodham Clinton as Secretary of State.

At a news conference today, President Barack Obama defended Rice -- who's been criticized by Republicans for saying in the days after the U.S. consulate attack in Benghazi, Libya, that the attack stemmed from a protest of an anti-Muslim video. They say she should have known that wasn't the case.

Obama told reporters today that if Senators John McCain and Lindsey Graham "want to go after somebody," then, in his words, "they should go after me."

Graham responded quickly, saying Obama shouldn't think "for one minute" that Graham doesn't hold him "ultimately responsible" for the deaths of the four Americans in Benghazi. But Graham also said he has "no intention of promoting anyone who is up to their eyeballs in the Benghazi debacle."

Graham, McCain and Sen. Kelly Ayotte of New Hampshire introduced a Senate resolution today calling for a select Senate committee to investigate the attack.

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