presidential candidate ads are required to have air time when they want it. Stations cannot turn them down. And the rates they pay are, by law, the lowest available on the station. Radio stations tend to limit the ads of a candidate to one per hour, but sometimes if the candidate is pushing hard for more time, the stations may double spot or run two per hour.
The problem I have with political ads is not the quantity, rather the quality. Regular advertisers in the media who sell products and services are required by the stations' clearance departments to provide scientific data on any claims they make in order to be cleared for air. Any statements that are indirect or implied claims must be substantiated as well. Impressions are subject to be scrutinized; an ad cannot mislead or create a wrong impression even though the actual text may not say something that is inaccurate.
But, political ads are not cleared for truthfulness or clarity or correctness. The messaging can say anything and not be kept from airing.
The amount of so-called negative ads that are being aired are massively misleading, and with the obama campaign outspending mcCain by over 2-1 margin, the false messaging that is being disseminated for the benefit of BO is creating voter behavior that is not legitimate.