Ad Hominem

An ad hominem ("to the person") dodges an argument by attacking the one making it. "You can't trust her claim about the budget — she's never even run a business." Whether she's run a business has no bearing on whether the budget figures are correct; the argument stands or falls on its own.^[1] It's persuasive because discrediting a messenger feels like refuting the message. (Note: pointing out a genuine conflict of interest can be fair — the fallacy is treating a personal attack as if it settled the argument.)