Customers with Conservative views can be rather outspoken about their views, and prone to act on their views. For a business to advertise on a Progressive station, or put posters in their window for events of a Progressive political group can result in some rather unpleasant tongue lashings from Conservative customers, and some flamboyant exits out the front door by Conservative customers who vow to never darken the door again.
It also works the other way too. Where Liberal customers can be rather out spoken about their views and be prone to act on those views. In the Wilmington Del. market (a blue county), two different AM's have had Rush's show (WDEL and WILM). Neither did well selling it. This is a moderate leaning left metro area, and from what I've been told by folks at both stations, is that local advertisers here are not comfortable advertising on Limbaugh or Hannity's show (probably Beck's show too now that one of our AM's is carrying it). Oddly enough though, even though this is a blue county, both WDEL and WILM beat the other in ratings during Rush's show, yet had trouble selling Rush's show here. When I listen in to Rush's show (now heard on WILM), that station plays a ton of PSA's and very few local spots during that show, yet they beat WDEL during that time slot. Yet, a talk station located 45 miles south in Dover WDOV (in a Red County) and one at the lower end of the state (a Red County) WGMD at Rehoboth Beach, Del, both get plenty of local spots during Limbaugh's show.
WDEL airs a local liberal talker during the time slot Glenn Beck is on WILM. WDEL has plenty of local spots, WILM with Beck, few to none. Yet, during AM drive, WILM has plenty of local spots even though their AM drive newsblock show has a conservative flavor to it that includes interviews with Fox News Radio reporters where the topic does get political. The show also gets good ratings.
So what works in one market may not work well in another, even with good ratings.