According to an October 22, 2015 article, “Advertisers May Suffer ‘Political Crowd Out’ As 2016 Elections Near” it is recommended to get in early or sit out in September and October. This suggestion is primarily focused on TV and radio advertisers where ad time is finite.
The article explains that presidential hopefuls will spend a record number of dollars this year with an estimate of 8.5 billion on broadcast TV. Read more here
