I would think that throwing money into the ad machine has diminishing returns after a certain point. When people hear the message, and they don’t like it, no amount of additional advertising is going to help...in fact it will have the opposite affect of reminding folks why they don’t like the message in the first place.
Money (spent on ads) != Votes.
Based on 35 years in the ad biz, I can assure you that no amount of ad expenditures can make people buy a product that a.) they've already tried and b.) didn't like.