TRYING TO UNDERSTAND A DOUBLE-STANDARD…. I’ve long tried to understand the double-standard when it comes to politicians and sex scandals — while common sense suggests they should be far more damaging to Republicans given the party’s moralizing, the opposite appears to be true.

Dave Weigel takes a crack at explaining this, noting three, recent, high-profile adulterers: Eliot Spitzer (D-N.Y.), David Vitter (R-La.), and Mark Sanford (R-S.C.). The two Republicans ran as evangelical, “family-values” conservatives, but got caught having sex with women who were not their wives. (In Vitter’s case, he was caught with at least two prostitutes.) Neither Republican resigned — on the contrary, Vitter appears likely to win another term, and Sanford hasn’t ruled out seeking public office again. Spitzer, meanwhile, resigned almost immediately after his sex scandal. As Dave sees it, the party identification is irrelevant.

What’s the difference? I have a bunch of theories. First, Spitzer was in New York, with a hungry and aggressive media — including national media — which had covered him as a star for years. Vitter and Sanford were relatively obscure to non-political junkies until their scandals. The second and, in retrospect, stupidest theory, keys off of this. It’s that Spitzer, the “cop of Wall Street,” was unusually hypocritical by buying a prostitute. The hypocrisy test is always subjective — I could agree that cost-cutting Sanford was a hypocrite, too.

The third theory is the one I’m most convinced of. It’s pure political advantage. When Vitter’s scandal erupted, a Democrat was governor of Louisiana, so there was no upside to getting him to resign — a Democrat would replace him. Sanford was leaving office, and no one in the GOP wanted his lieutenant governor — a much-disliked pol who ended up coming in last in the 2010 gubernatorial primary — to replace him. But Spitzer’s implosion happened when Democrats had control of most of the state, were headed to a landslide fall election, and saw him, already, as their biggest liability. Personally, Democrats in Albany were butting heads with him. He didn’t resign because of the scandal. He resigned because no one wanted him to stay.

That’s fairly compelling, but there are some examples that run counter to Dave’s theory. The most striking is Nevada Sen. John Ensign (R), who’s in the midst of a sex/corruption/ethics scandal. If he stepped down to focus on his legal defense, a Republican governor would fill the vacancy. For that matter, Ensign has never been wildly popular or influential in the Senate GOP caucus, so forcing him out after he disgraced himself — and became the subject of a federal criminal investigation — would have made perfect sense as far as “political advantage” goes.

But Ensign didn’t resign, and Republicans didn’t try to push him overboard. At this point, despite the humiliation, the FBI probe, and the Senate ethics investigation, Ensign remains a Republican senator in good standing — and he’s taking steps to seek re-election in 2012.

I like Dave’s explanation, but the examples that run counter to the theories are numerous. Rudy Giuliani, for example, was in New York with “a hungry and aggressive media — including national media — which had covered him as a star for years,” but when he cheated on his second wife with his third, and marched in a St. Patrick’s Day parade with his mistress, the idea of him resigning never really came up.

When Nevada Gov. Jim Gibbons (R) strayed from his wife during his time in office, the was a political advantage to forcing him out — Nevada’s lieutenant governor would have kept the office in Republican hands — but it didn’t matter and he’ll serve out the remainder of his term.

Democrats caught up in sex scandals — Spitzer, John Edwards, Jim McGreevey, and to a lesser extent, Eric Massa — tend to quickly resign and avoid politics. Republicans — Vitter, Ensign, Sanford, Gingrich, Giuliani — prefer a far different approach, reject the idea of being permanently disgraced, and the GOP doesn’t seem to mind.

I can appreciate why IOKIYAR seems like a lazy cliche, but I’m not convinced it’s wrong.

Steve Benen

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.