snake oil salesman
Someone who sells, promotes, or is a general proponent of some valueless or fraudulent cure, remedy, or solution. (Can also be formed as "snake oil saleswoman" if referring to a woman, or "salesperson" to be gender neutral.) I find it hard to believe anyone would fall for those snake oil salesmen on TV selling holistic medicines and therapies. A lot of people have been swayed by the presidential candidate's plan for economic growth, but if you ask me, she sounds like a snake oil saleswoman.