Political ads on the airwaves have been so pervasive this year that voters in battleground states probably see them in their sleep. But when a political spot pops up while surfing the Web, there's a good chance it's aimed right at you.

The practice is called microtargeting and like a lot of marketing techniques on the Internet aimed at identifying consumer tastes and behaviors, it is an information-age approach that is helping change how political groups identify and interact with voters.

Moreover, microtargeting may give pollsters, campaigns and interest groups a sharper idea of how candidates and issues may fare at the ballot box, raising concerns about personal privacy in a medium where government regulation is minimal.

In fact, "there is none," said Chris Calabrese, legislative counsel for the American Civil Liberties Union.

"Anonymity has been crucial to our political process. It's the reason for the secret ballot, it's the reason the Federalist Papers were anonymous," he said.

Surfing the Web leaves a trail of browser history that allows marketing companies to glean insight into personal interests.

Do you read The New York Times or watch Fox News? Do you have children? Do you shop in high-end stores or hunt for bargains on eBay? Do you support the Sierra Club or Club for Growth?

Political strategy firms like Democratic DSPolitical and Republican CampaignGrid are gathering or buying up that data. They then match it to the publicly available voter rolls that were digitized as a part of a new federal law aimed at efforts to help improve voting procedures after the ballot controversies of the 2000 election.

What these firms receive is detailed information about how often a potential voter has cast a ballot in addition to data on what they read, where they shop and other consumer behavior tracked for decades off line.

Jim Walsh of DSPolitical said the company has so far aggregated more than 600 million cookies -- or tags on Internet user IP addresses that track movements online -- and has worked to match them against lists of some 250 million voters in the United States.

This all is aimed at helping them determine how someone might vote and then reaching them wherever they go online.

It is so efficient and such a natural extension of direct mail that Walsh called the way microtargeting is being used today "inevitable."

In response to privacy advocates, CampaignGrid President Jordan Lieberman and Walsh said they aren't doing anything that hasn't been done before.

"The data has been commercially available data for years -- we're not targeting you by who you voted for; we're targeting you if you tend to vote or participate in the democratic process," Lieberman said.

And he said these strategies infringe less on privacy because they don't use names or physical mailing addresses like direct mail.

"The reality is that we are more focused on privacy and we have more privacy protections than direct mail ... has used for decades," Lieberman said.

This they said is because lists generated from browser histories are stripped of any personal information before they are used to target potential voters. Both companies said they use a third party vendor to remove that data and match the files.

Lieberman wouldn't identify CampaignGrid's vendor, calling it "part of the special sauce."

DSPolitical and CampaignGrid aren't the only ones in the game.

Google, Facebook and other data powerhouses are also in on the action, albeit in a different way.