ENSIGN, WHOA…. Under normal circumstances, I wouldn’t much care what Sen. John Ensign (R-Nev.) does in his personal life. What he does in his bedroom is his business.

But the larger context of this story matters a great deal. Stupid personal mistakes are easily overlooked; breathtaking hypocrisy isn’t.

Sen. John Ensign (Nev.), considered a rising star in the Republican Party, yesterday acknowledged an extramarital affair with a former campaign staffer who is married to one of the lawmaker’s former legislative aides.

Ensign, a member of the Senate Republican leadership, disclosed the affair at a hastily arranged news briefing in Las Vegas, his home town…. “I deeply regret and am very sorry for my actions,” Ensign said, reading from a prepared statement and leaving without taking questions.

The details of the affair are rather salacious — Ensign was in a relationship for much of 2008 with a woman on his staff, who was married to a man who was also on his staff — but those circumstances are really only relevant to the people directly involved in the relationship.

Of far greater interest is Ensign’s hypocrisy. When Bill Clinton’s adultery came to public light, Ensign not only voted to remove the president from office, but insisted the president should resign as a result of the personal scandal. When former Sen. Larry Craig was caught up in a sex scandal, Ensign not only called for Craig’s ouster, but led the charge against him.

Ensign has also been a fierce opponent of marriage equality, and supported a constitutional amendment to ban gay marriage. In 2004, the Nevada Republican lectured his colleagues, “Marriage is the cornerstone on which our society was founded. For those who say that the Constitution is so sacred that we cannot or should not adopt the Federal Marriage Amendment, I would simply point out that marriage, and the sanctity of that institution, predates the American Constitution and the founding of our nation.”

And did I mention that Ensign is a longtime member of the Promise Keepers, a conservative evangelical group that promotes strong families and marriages?

Few really care about Ensign’s private life. The story is relevant only insofar as the Republican lawmaker has spent much of his career touting “families values” and using his office to promote his version of sexual morality — with standards he doesn’t apply to himself.

For what it’s worth, his previous statements regarding others notwithstanding, Ensign has said he does not intend to resign. He is not up for re-election until 2012.

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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.