Elections were once decided in the smoke-filled rooms of party bosses. Then they were waged in war rooms of political operatives. Today, they're won in computer caves.

Inside the Cave is a must-read look at the Obama re-election campaign's digital operation. The Obama "cave" at its Chicago headquarters buzzed with more than 50 analysts who used reams of data to predict the individual behavior of tens of millions of Americans voters. It's not hyperbole to suggest the Obama campaign may have known who you were going to vote for before you did.

As Sasha Issenberg found in his own reporting, the Obama campaign created a system "that predicted the behavior of individual humans. The campaign didn't just know who you were; it knew exactly how it could turn you into the type of person it wanted you to be."

To do this, Team Obama didn't hire typical political staffers. Instead they combed their donor rolls for data geeks in Silicon Valley and Wall Street who were willing to quit their jobs for 18 months to help re-elect the president. The new recruits were part of a formidable team of data analysts who were used, in the words of campaign manager Jim Messina, "to make sure we were being smart about things."

They used analytics to improve every aspect of the campaign — from internal polling to predicting if emails would be opened by supporters. Every night the campaign made 8,000 to 9,000 phone calls to test their assumptions with real survey data. They tested everything, questioned their assumptions, and then tested again.

Said one Obama operative after the campaign: "We basically found our guts were worthless."

And in the process, they reinvented the modern political campaign.