ANOTHER ‘FAMILY-VALUES’ REPUBLICAN RESIGNS AFTER SEX SCANDAL…. In the House of Representatives, Christian conservatives and religious right groups have no more reliable an ally than Rep. Mark Souder (R) of Indiana. It makes these shocking revelations all the more interesting.

Indiana Rep. Mark Souder (R) will resign his congressional seat after an affair with a staffer came to light, he said in a statement this morning.

“It is with great regret I announce that I am resigning from the U.S. House of Representatives as well as resigning as the Republican nominee for Congress in this fall’s election,” said Souder.

“I sinned against my God, my wife and my family by having a mutual relationship with a part time member of my staff,” added Souder. “I am so shamed to have hurt those I love.”

Every time a conservative Republican gets caught up in a sex scandal, it carries a little extra punch — the GOP, after all, claims the moral high ground as the party of “family values” — but Souder’s scandal is especially humiliating. The Indiana Republican, after all, has made the “fight to uphold traditional values” the centerpiece of his professional life. His official website declares, “The family plays a fundamental role in our society…. I am committed to preserving traditional marriage, the union of one man and one woman… I am committed to fighting the assault on American values.” Souder has been especially active in fighting against gay rights and for abstinence-only funding

Oops.

At this point, Souder is quitting Congress altogether, not just announcing his retirement. The timing is a little awkward for the Indiana GOP — Souder just won a tough primary two weeks ago — but Dave Weigel has heard that Hoosier Republicans can replace Souder on the ballot when the state party hosts its convention in mid-June.

But then there’s the larger context: those “family-values” Republicans sure do have a lot of sex scandals, don’t they? It’s getting difficult to keep track of them all. Souder is the newest, but his humiliation comes on the heels of Sen. John Ensign’s (R-Nev.) scandal. That came to light around the same time as Gov. Mark Sanford’s (R-S.C.) sex scandal, which came soon after Gov. Jim Gibbons (R-Nev.), which itself followed Sen. Larry Craig (R-Idaho).

If we look back a little further, we also find disgraced former House Speaker Newt Gingrich and former NYC Mayor Rudy Giuliani. If go back a little more, names like Vito Fossella, Tim Hutchinson, Henry Hyde, Dan Burton, and Bob Livingston also come to mind. And those are just the office-holders.

For the better part of a generation, the Republican Party has demanded higher moral standards of all of us, while failing to meet these standards. It’s far easier for the public to tolerate personal mistakes and human failings than it is to accept shameless hypocrisy.

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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.