Walker was already a scandal-plagued candidate (as was Warnock, FWIW.)
Personal use of campaign funds and allegations of domestic violence. Both Warnock and Walker have the "scandal" tag in FiveThirtyEight's model.
Interestingly enough, the abortion drama with Walker wouldn't be enough to meet 538's threshold on its own (since there's nothing illegal about paying for your girlfriend's abortion.)
The cited so-called "scandal" involving Warnock is extremely tenuous, and even the disingenuous Politico article just says that there are "questions" re his use of campaign funds to defend him in a lawsuit. It's likely that people wouldn't file frivolous lawsuits against him if he were just a private citizen, so Warnock's argument that it's a legitimate use of campaign funds seems valid. And anyhow, in total the so-called questions surround the use of $1,183. I cannot fathom a less interesting or smaller "scandal."
His ex-wife's allegation of one specific instance of violence also was determined by police to be without merit.