By now, you're probably aware that much of your online behavior is tracked, logged and probably sold to third parties so that marketers can better target you with ads. Targeted advertising has become a fixture of the Web, in part because Internet browsing generates a wealth of useful data that's easily studied.

Television is a bit of a different story. Take traditional, over-the-air broadcast. For advertisers, it's the media equivalent of a sawed-off shotgun: not terribly accurate, but extremely effective when it does find the mark. Now, however, targeted advertising on television has taken a big leap forward. And it could represent the next evolution in data-empowered politics.

Dish Network and DirecTV on Monday announced a plan to jointly give political advertisers the ability to microtarget their ads down to the household level. That means that any of over 20 million homes in the United States will soon start getting highly personalized campaign spots that were meant just for them.

Here's how it works: While your set-top box is idle, it'll tune into a channel that's playing the ad you're meant to see. It'll record the ad using DVR, then insert it into your regular programming while you're watching a show — replacing or bumping the ad that was supposed to air instead. This can be replicated for any household that subscribes to Dish or DirecTV, so a political strategist can pick you out and feed you a unique message.

Some TV targeting is possible already. Individually, Dish and DirecTV have offered "addressable advertising" on their own networks for about two years. But, says Carol Davidsen, a former media targeting director for President Obama's 2012 campaign, it's never been available at this scale. That's why political operatives find this exciting: It gives them access to a far larger pool of potential test subjects for their material. That's right: Satellite TV subscribers are about to be subjected to the same rigorous testing that informed the Obama campaign's use of catchy e-mail headers.

Though this might inspire fantasies of a different ad that's custom-made each for seniors, soccer moms and single youths, the reality is that most campaigns won't be able to afford it. It's simply too expensive for your average campaign to get actors or B-roll for multiple ads.

"It's more for testing creative and testing the persuasiveness of an ad" than trying to convince undecided voters, said Davidsen in an interview.

For now at least, addressable advertising will be mainly used on a small scale to evaluate two versions of the same ad before a campaign embarks on a much larger media buy. Most likely, strategists say, the ads will be followed by phone calls asking viewers about the impact of what they saw — adopting what are essentially polling methods. That's actually a major improvement over the current method of focus grouping content in small, less-standardized settings. The benefit of smushing Dish and DirecTV's customer base together is that the combined sample size is much larger than before, and more representative.

But in the long run, statewide campaigns will also be using the feature to better target that core message to the people they really want to reach, all while ignoring those that can't be persuaded. Think of it this way: If you know that a certain neighborhood is home to 100 people, a quarter of whom are on your side already and a quarter of whom are voting for the other guy, that leaves 50 people who might be susceptible to your message. Rather than blanketing the whole neighborhood with your ad and hoping it reaches the right 50 people, it's more useful to know with certainty which homes you ought to target. Once you do, you can follow up and identify who will be more easily swayed in future rounds, and the whole system repeats itself.