Re: What can you do when another man is moving in on your wife?
My bit is functioning under the notion that your partner is successfully being lured away.
It's a two front battle. Nobody decides to cheat out of the blue - the groundwork is set between you and your partner long before Mr. Scoop comes along. And lets face it, if the relationship issues don't get sorted out, it won't matter how many suitors you have to fend off ... you've lost.
I think we get caught up in the idea of civility and appropriateness, which is why it's easier to be furious about another man moving in on your partner - but instead try to shore up the relationship. My opinion is, at this point you are already too late, and quite possibly, you are better off going after TOM in an effort to squelch any blossoming romance.
I don't want to get into the whole alpha/beta thing, but there is a lot to be said for being assertive and unafraid of confrontation. Confrontation needn't mean an ass-kicking either.
At the good old evolutionary level, I don't doubt that your partner would raise a stink if you make it clear that you are going to confront the other man. But ... actually doing so, sends a very clear message, and one that despite her protests, at some level is going to change her perception of you.