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Cablevision has been bought up by European telecommunications giant Altice. - 

If you live in a state with a close race in this year's midterm elections, you know that candidates are carpet bombing the air waves with TV ads. But candidates and campaigns are increasingly airing their ads over cable instead of their local broadcast station, for a bunch of reasons, some specific to this year.   

“There’s just not a lot of competitive House races," says Ken Goldstein, a professor of political science at the University of San Francisco. "We’re sort of in a dead-ball year, in terms of House races.”

And the House races that are close are in big cities, where it’s not efficient to advertise on local TV. Plus, there aren’t as many competitive races for governor, and those are mostly fought on local airwaves. 

But long-term trends also give cable an edge over local TV.

“Now we can do targeting that we couldn’t do before,” says David Karpf, an assistant professor in the School of Media and Public Affairs at George Washington University.  

Karpf says local broadcast TV is broad and scattershot. But cable set-top boxes tell campaigns exactly what voters are watching, so campaigns can tailor their ads.

“So that would allow them to deliver an advertisement to one neighbor, and a different advertisement to a different neighbor, ideally,” he says.

For example, voters in one district might like watching re-runs of old shows like Mork and Mindy. Of course that show is from back in the '80s, before cable started taking political advertising away from local broadcasters.   

Don't be mistaken, local TV still rakes in the most cash. But it’s only grown a little from the last midterms, in 2010.

“Local TV’s heyday is over in that these great gains we saw in local TV ad spending for politics, cycle over cycleprobably slowing and eventually will plateau,” says Elizabeth Wilner, senior vice president for political advertising at Kantar Media.

Spending for political ads on cable this election, meanwhile, is expected to nearly double.