Political ad spending has fallen this year. Image source: Hillary Clinton. 

What happened

Shares of Sinclair Broadcast Group Inc (SBGI 0.41%) closed down 9.4% today after the broadcaster conceded that the political campaign season hasn't been as lucrative as it expected it to be.

So what?

In a press release, Sinclair lowered its third-quarter guidance, saying it now expected revenues of $637 million to $638 million, down from a previous range of $649.2 million to $663.2 million. Expected political spending dropped from $58-$68 million to $46 million. CFO Chris Ripley explained, "Political is the most difficult part of our revenue to estimate given that advertising time is typically purchased with only a couple of days' notice prior to the ads airing." He added that the company had anticipated slower presidential ad spending due to late fundraising by the Trump campaign, but it was also affected by widening polling in the Ohio senate race, which makes advertising less necessary, and the decision by one advertiser to focus on organizing voters rather than campaign funding.

Now what?

Sinclair pulled its full-year political revenue forecast of $260 million to $280 million, though management was hopeful that the tightening presidential race would cause an increase in ad spending for the remaining weeks of the campaign. It also said its forecast of low single-digit revenue growth in its core advertising unit remained intact.

Peers Gray Television (GTN 2.56%) and E.W. Scripps (SSP -0.94%) also fell on the news, as those broadcasters are affected by the same trends as Sinclair. Political campaigns are a boon to broadcasters, but a shortfall of $10 million to $20 million in the case of Sinclair does not seem to warrant a 10% sell-off. If the stock continues to fall, I'd consider it a buying opportunity for an otherwise solid company like Sinclair.