Iowa, New Hampshire, and South Carolina have marked the route to the White House for more than a generation. But in 2016, the path to the presidency will run through new territory—your Facebook news feed.

As the race begins in earnest, the world’s largest social network is emerging as the single most important tool of the digital campaign, with contenders as different and disparate as Hillary Clinton and Ben Carson, Rand Paul and Bernie Sanders, all investing in the platform already.

Thanks to powerful new features unveiled since the 2012 campaign, Facebook now offers a far more customized and sophisticated splicing of the American electorate. And, for the first time in presidential politics, it can serve up video to those thinly targeted sets of people.

That unprecedented combination is inching campaigns closer to the Holy Grail of political advertising: the emotional impact of television delivered at an almost atomized, individual level. It makes the old talk of micro-targeting soccer moms and NASCAR dads sound quaint.

“I can literally bring my voter file into Facebook and start to buy advertising off of that,” says Zac Moffatt, who was Mitt Romney’s digital director and whose firm now works for Rick Perry’s campaign and Scott Walker’s super PAC.

“We use Facebook more than any single tool,” says Wesley Donehue, a top digital strategist for Marco Rubio, speaking about both his political and corporate clients. “The level of targeting has gotten so sophisticated, allowing us to drive different messages to different audiences. I mean, the amount of content we’re pumping out on Facebook right now is just unbelievable.”

With 190 million American users, Facebook’s wealth of information about its members is unmatched: identity, age, gender, location, passions—much of which is coughed up voluntarily. But it doesn’t end there; Facebook has a far more complete picture of its members than even what they’ve typed in themselves. Through partnerships with big data firms, like Acxiom, the site layers on a trove of behavioral information, such as shopping habits.

What that means is that Facebook, with its reach across a huge swath of the U.S. electorate, can pinpoint individual voters at the most granular of levels. And that’s why campaigns are buying their way in, reshaping not only campaign budgets but how the political battle itself is fought and won.

“The secret is out,” says Alex Skatell, an influential GOP digital strategist who is not affiliated with any 2016 campaign. “Facebook is kind of the first place people go now.”

ALREADY, DIGITAL operatives are modeling the universes of likely Iowa caucus-goers and potential New Hampshire primary voters and uploading those models into Facebook. Then, they match them with Facebook profiles of actual voters in those states. (Strategists say match rates can run as high as 80 percent.) It’s a powerful feature—custom-designing the audience for your ads to coincide with the voter rolls—that didn’t exist four years ago.

“We are guaranteeing you will reach the right person at the right time and eliminate the waste that you might find in email marketing, certainly in TV advertising,” says Eric Laurence, who is in charge of political advertising on Facebook. “That’s really the power of Facebook targeting.”

The precision and price of such spots, to borrow a favorite Silicon Valley aphorism, threatens to disrupt the way campaigns are run, cutting down on inefficiencies and democratizing some of the data and targeting leaps pioneered by the Obama campaigns.

A statewide television buy in Iowa, for instance, reaches more than 3.1 million potential viewers. But only 121,000 people actually turned out at the Republican caucuses in 2012. So instead of blanketing the state, Facebook allows campaigns to target only those who they believe to be likely caucus-goers and then to fragment that universe further into a thousand smaller subsets. One ad could run to students at the University of Iowa and another to those at Iowa State. Or just alumni. Or female alumni. Or alumni who “like” Rush Limbaugh. In Des Moines.

“Think about how powerful this is. This is so, so powerful, and I honestly think it’s still underused,” says Vincent Harris, Paul’s chief digital strategist. “And it’s cheap. It’s so cheap. I am getting Facebook video views for one cent a view—one cent a view! … It’s a fundraising tool, it’s a persuasion tool, and it’s a [get-out-the-vote] tool. It’s a way to organize, too.”

“Facebook is actually everything,” Harris adds. “And this is what scares people.”

AT THIS PHASE, the campaigns are mostly mining Facebook for new donors.

“Any national campaign that we work with, we recommend Facebook advertising as part of acquisition strategy,” says Keegan Goudiss, a Democratic digital strategist whose firm, Revolution Messaging, is helping the Sanders team. Goudiss says prospecting for donors through Facebook typically pays three-to-one—that is, three dollars raised for every dollar invested, though the payout often can take as long as 12 months.

In a remarkable statistic Facebook likes to tout, the 2013 campaign of Terry McAuliffe for Virginia governor, run by Robby Mook, now Clinton’s campaign manager, immediately recovered a whopping 58 percent of its Facebook acquisition costs by linking new email subscribers to online contribution forms.

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