Dude, ANYthing could be considered to be a campaign expense if you want it to be.
Sir, Anything that is done for the purpose of aiding the campaign is a campaign expenses. And you are correct if you believe that this is a very broad definition, but it is intended to be. If you buy a round of coffee for your campaign staff, that is a campaign expense. If someone else buys coffee for your campaign staff that is an in-kind donation to your campaign and needs to be recorded as such.
Protecting his wife from a porn actress's slanderous claim is hardly one of them.
And this was an issue that was raised in the trial. It is my opinion that this money was paid to aid the campaign, it might be your opinion that this money was paid to "protect his wife". But our opinions do not matter. There was a trial, the prosecution presented their evidence and made their arguments, the defense presented any evidence they wanted to present and made their arguments, and then the Jury reached a verdict.
Our opinions do not matter, the twelve opinions of the Jurors do. And in their opinion this money was paid for the purpose of aiding the campaign.
That is the reality of the situation. You can decide to accept reality, or not.