In response to those that say infidelity doesn't matter in public office, I disagree.
Marriage vows are very important, more important than a temporary term in office. I say this meaning the vow itself is more binding (unless you went with non-traditional vows about loving your mate more than chocolate.) So to treat such an important vow with disregard is a reflection on that person and how they will view other vows and promises.
I realize that each case is different and the circumstances for each will say a lot. But I do think it is something that deserves attention.