Wait until you hear Edwards' defense; it's a doozy. Something along the lines of if the truth about his double-life got out, it would have killed his campaign, so in that vein, the money was spent on a campaign item.
Where he actually failed was in not disclosing receipt of the money and on what it was spent; radio pundits today speculated that had he done that, claiming it as a gift, he'd be in the clear. I dunno.
What I haven't been able to figure out is why Edwards? The Dems don't usually do this to their own, especially when sex is involved -- and let's face it, Edwards is now a nothing-burger -- so whose political/promotional nest is being feathered here?