This year’s Presidential election looks set to be, by a long shot, the most expensive ever. The Romney and Obama campaigns (and their allies) have already spent more than four hundred million dollars on television ads, and are expected to shell out six hundred million more in the next seven weeks. But the most important struggle between the campaigns is taking place elsewhere: in the hands-on, door-to-door fight for votes, called the “ground game.” And, as Sasha Issenberg shows in his enlightening new book, “The Victory Lab,” the ground game has been revolutionized in recent years by technological innovation and clever experimentation, to the point where it may well have a bigger impact on Election Day than all those millions in ads.

Illustration by Christoph Niemann

Even in today’s money-soaked politics, all campaigns have limited resources of money, time, and manpower. Campaigns fail if they waste resources courting voters who are unpersuadable or already persuaded. Their most urgent task is to find and persuade the few voters who are genuinely undecided and the larger number who are favorably disposed but need a push to actually vote. Companies have long gathered data to break down their customer base into specific segments. Now political parties have become adept at micro-targeting, too, using data on shopping habits, leisure activities, voting histories, charity donations, and so on, in order to pinpoint likely supporters and the type of appeal most likely to win them over. In 2004, the G.O.P. bought ads on the Golf Channel, because Karl Rove’s data told him that golfers were more likely to support Bush than Kerry. And, as Issenberg documents, prospective Republican voters received different, and carefully targeted, versions of Bush’s campaign positions depending on their neighborhood, or even their street: some were reminded that Bush was pro-life; others read about his pro-immigration positions. The 2008 Obama campaign was even more sophisticated, using a custom-built, constantly evolving algorithm that incorporated hundreds of variables in order to predict any given voter’s allegiance and level of enthusiasm. It sometimes seemed to campaign operatives that the algorithm knew what voters thought before the voters themselves did.

This kind of precision changes the nature of campaigning. Instead of just flooding the zone with TV ads and hoping that the right people see them, campaigns can send flyers to only a few hundred people, say, or buy bus ads on one particular city line. Micro-targeting is hardly perfect—last week, I got a letter asking me to donate to Sheriff Joe Arpaio, in Arizona—but when it works it allows campaigns to speak to voters directly and cost-effectively.

Of course, even if you find the right voters, and make the right appeals to them, there’s no guarantee that they’ll show up at the polls. Campaigns have always worked hard to get out the vote on Election Day, but they didn’t always work smart. As Issenberg shows, that has changed, thanks largely to the efforts of the political scientists Alan Gerber and Donald Green. Randomized, controlled experiments, common in academia, were virtually unknown in politics. But, starting with the 1998 midterm elections, Gerber and Green experimented with various get-out-the-vote techniques. The first experiment compared the effectiveness of calls from a paid call center, a piece of direct mail, and a home visit. Having people knock on doors, it emerged, boosted turnout by almost nine per cent—far more than anyone had predicted, and easily sufficient to swing an election. Impersonal techniques—generic direct mail, phone calls from paid, script-reading workers—did little to encourage voting, but chattier, more inquisitive phone calls from volunteers were effective. Later experiments showed that social pressure could also boost turnout. For instance, Gerber and Green sent people postcards telling them that their neighbors would be informed after the election of whether or not they had voted—which made turnout soar. And positive reinforcement works, too. Just thanking people for having voted in the past significantly increases the chance that they’ll vote again.

From one angle, these successful tactics seem quite mundane. But that’s what’s striking: political campaigns long neglected useful strategies, because they never did the research to find out what really worked, and because they were obsessed with, as Issenberg puts it, “changing minds through mass media.” And of course the homely labor of knocking on doors and sending postcards wasn’t as valuable before the egghead work of micro-targeting could tell you which doors to knock on. In that sense, a well-run ground game is a perfect blend of the technological and the concrete, of the future and the past.

A great ground game can’t make up for dismal fundamentals or a terrible candidate. Rick Perry was a fervent believer in victory-lab techniques, but that couldn’t help him string coherent sentences together. Yet such techniques can make a huge difference on the margin, and in close elections that’s all the difference that matters. This doesn’t seem to bode well for Mitt Romney. Although he pioneered the use of micro-targeting in his Massachusetts gubernatorial campaign—targeting premium-cable subscribers, who were thought likely to favor his technocratic approach—he’s now running a very TV-intensive campaign. The Obama campaign has put far more into the ground game, and it has the advantage of the experience and the data it gathered last time around. Romney will likely spend more and buy more ads, but that may not matter if Obama ends up with more knocks on the door. ♦