For me, it's not even a moral issue. It's a very practical issue regarding susceptibility to blackmail.
This was true for Clinton just as much as it was for Kerik. If a foreign intelligence agency had cottoned on to Monica before she became public, they could have led Clinton around by the nose. He jeopardized the security and independence of the whole country to sate his own selfish desires.
Anyone who cheats on his wife is unfit for a position of public trust, and you don't have to be a blue-nosed Bible thumper to see why.
Yes, Mr. Clinton amply demonstrated your point, and on this much I had to agree with Mr. Perot. If a man's wife can't trust him...