THE RELIGIOUS RIGHT’S ‘WALL OF SILENCE’…. Most of the relevant players have weighed in on South Carolina Gov. Mark Sanford’s (R) personal and professional difficulties, but Dan Gilgoff reports there’s one group whose silence stands out.

One week after Mark Sanford admitted to his affair with an Argentine woman — and a day after he called his mistress his “soul mate” and acknowledged further indiscretions — I’m struck by the total silence of pro-family groups.

The Family Research Council has been completely quiet on the South Carolina governor’s affair. So has Concerned Women for America. Ditto for Focus on the Family.

The wall of silence is all the more striking given that 10 Palmetto State senators in Sanford’s own party have called for him to step down. Does the pro-family movement burn up credibility if it looks the other way when Republican allies own up to extramarital affairs?

That’s certainly a reasonable question, though I’m not at all sure the religious right still has “credibility” in reserve.

Either way, the movement’s silence is striking. The afternoon Sanford admitted his affair, the Family Research Council, which had invited Sanford to be a featured speaker at its 2009 Values Voter Summit, moved with lightning speed to remove the governor from the guest list.

But that obviously isn’t a condemnation. While religious right groups rarely hesitate to issue moralistic denunciations about events of the day, they’ve somehow managed to give Sanford a pass.

Gilgoff flagged this gem from a book Family Research Council President Tony Perkins wrote: “As long as we as Christians are willing to tolerate or overlook duplicity in our self-identified party, it will be clear to the world that our allegiance is to a party and not the truth, regardless of what we claim…. [I]f we are ever to speak as the moral conscience of the nation, we must consistently stand for a clear set of values and principles, no matter if that leads to a temporary loss of political power.”

I realize that Sanford was as close an ally to the religious right movement as any governor in the country. But if these groups expect to lecture the rest of us about morality and family values, they should at least offer some criticism of their close ally.

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Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.