Republican candidates Gingrich and Cain refuse to state Mormons are Christians

Bob Schieffer asked Republican presidential candidates Herman Cain and Newt Gingrich whether Mormons were Christians on Face the Nation
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Schieffer: ...  I want to ask both of you -- You both spoke to the big conservative values conference last week but the preacher who introduced Rick Perry kind of stole all the headlines because he told reporters that Mormonism is a cult and that Mitt Romney is not a Christian. Mr. Gingrich, should that be a part of the discussion?
Gingrich: No, I think that none of us should sit in judgment of somebody else's religion and I thought it was very unwise and very inappropriate.
Schieffer: Do you think that Mitt Romney is a Christian?
Gingrich: I think he's a Mormon and Mormons define themselves as a branch of Christianity.
Schieffer: How about you, Mr. Cain. What's your thought on this?
Cain: I feel the same way. We're not running for theologian in chief. We're running for president of the United States of America. What I believe is that the American people want to know: what are your values? What are your principles? Because your values and your principles may impact how you make decisions. But not get into the specifics of your chosen religion.
Schieffer: Do you think Mormons are Christians?
Cain: I believe that they believe that they're Christians based on their definition but getting into whether or not they're more Christian than another group, I don't think that's relevant to this campaign.
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Background,
excerpt from Rick Perry Endorser Calls Mormonism A 'Cult' And Planned Parenthood A 'Slaughterhouse For The Unborn', abc news.  Note Perry later disavowed Jeffress statement.

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Rick Perry spoke at the Values Voter Summit, a gathering of hundreds of social conservatives... but the evangelical pastor who introduced him stole the show, sparking a controversy in the process.
It was no ordinary opener from the prominent Southern Baptist Convention leader, Pastor Robert Jeffress, who endorsed Perry on Friday. ...

"Do we want a candidate who is a good, moral person — or one who is a born-again follower of the lord Jesus Christ?"
Jeffress called Perry a "genuine follower of Jesus Christ." The pastor did not mention Perry's rival Mitt Romney by name, but he told reporters after his remarks on Friday that Mormonism was a "cult."
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Excerpts of Pastor denies remarks against Romney were 'bigotry' (CNN)
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Jeffress himself fired back later in the day, arguing that his statements were not bigoted. He cited John Jay, the first chief justice in the United States, who said that Christians have a "duty" to select other Christians as the country's leaders.
"I hardly think John Jay was a bigoted person," Jeffress said.
When asked about Article 6, paragraph 3 of the Constitution, which bans a religious test for the presidency, Jeffress said the clause only applies to the government, not individuals.
"We have every right to impose a litmus test on the kind of person we prefer," he said. "You can show preference without being a bigot and certainly without violating the Constitution."
CNN's Kyra Phillips on Saturday pressed Jeffress on whether religious beliefs should trump competence in presidential candidates.
"Yes," Jeffress said. "To religious people, religion matters."