Comcast (NSDQ: CMCSA) execs said the company posted double-digit growth in auto, health care and retail advertising in Q2. As the fall elections approach, political is also expected to be a big revenue driver for its ad business this year. But for the moment, advertising is a small part of Comcast’s business, said COO Steve Burke during the start of the earnings call. Advertising is only a $2 billion business for the cable operator annually — just a fraction of the $35 billion in total revenue that Comcast brings in. While the costs of completing the purchase of a stake in NBC (NYSE: GE) pulled Comcast’s profits down in Q2, it’s a small short-term price for what the company views as a long-term gain. With the addition of NBC, Burke said that will change, as Comcast expects that merger to result in roughly $10 billion in advertising revenue.