That remains true for 'early buys' of media by direct candidate and political party purchases. As well the various media outlets are only required to allocate a percentage of their available space for the discounts although they can choose to do more as they see fit.
However, the low-cost rates do not apply for the indirect advocacy groups like PACs and 501 groups, they generally pay close to normal pricing. Additionally, 'emergency' time buys (gaffe responses) and buys after the percentage allocation has been committed will go for higher rates than the discounted.
The latter rule was one of the numerous obstacles for Romney in 2012. Since Obama was the undisputed Democrat candidate, he could immediately spend general election funds throughout the summer to attack Romney and make the 'early buys' that would exhaust the discount space availability. When Romney was finally confirmed as the GOP candidate at the Convention in September, he was 3 months behind the Obama campaign AND had to spend more for the same ad space in the markets that were considered competitive. This is the reason that you will probably never see another late-summer political convention. They all will be moved to late May and June.
Thanks for the clarification - on the PACS- and as I understand it, some of the Mitt PACS gladly paid the higher rate because they were working off a commission of the buy (how agencies get paid) - so if they bought a million, they retained 100-150 grand whatever, whether that million was at a good rate or a bad rate.
I heard that’s how Romney got less bang for the buck than he should have.