It’s my good luck to have learned how to cover campaigns in Philadelphia. Politics in an old, big city has remained a wondrously physical affair. The campaign operatives I talked to tended to brag not about the size of their television ad buys but about how many election day workers they would have on the street and how many vans they had rented to drive voters to the polls. I savored election days not as a twelve-hour lull between the frantic close of a campaign and its result, but as the occasion where electioneering machinations were forced out in the open. I spent those days taking long walks on city streets. For one primary, starting just across the city line in Delaware County when polls opened and winding my way by dusk nearly to the Montgomery County border near Oak Lane, I traveled around twenty-four miles, nearly a proper political marathon—stopping along the way to check in on polling places and union staging areas, and to talk to party committeemen and ward leaders.

Philadelphia offered a real education in political tactics at their most tactile, at what I only years later appreciated had been a transformative moment in the way campaigns counted, targeted, and mobilized votes. Those experiences instilled in me a sense that campaigns were more than a procession of speeches, ads, debates, and press conferences, in a way rarely reflected in political journalism. So I owe a lot to my friends and sources in the Philadelphia political world, particularly Nathaniel Parks and Harry Cook, who gave me my earliest lessons in the rudiments of field and voter contact, even though I wouldn’t have had the language to describe what I was learning that way. Others have been generous with their time and wisdom then and since, including Tom Lindenfeld, Mike Roman, Neil Oxman, J. J. Balaban, Doc Sweitzer, Sam Katz, Jim Baumbach, Maurice Floyd, Michael Bronstein, Mark Nevins, Ken Smukler, Maureen Garrity, Al Spivey, Elliott Curson, Eleanor Dezzi, Rebecca Kirszner Katz, Brian Stevenson, Mark Alderman, Micah Mahjoubian, Stephanie Singer, Tracy Hardy, Appollos Baker, John Hawkins, Chris Mottola, Commissioner Josh Shapiro, and Congressman Bob Brady.

The Boston Globe allowed me to cover the best presidential campaign I have any right to have lived through, let alone track across thirty-eight states and six countries. I am grateful to Peter Canellos for making me a newspaperman, and to Marty Baron for taking a chance on someone who had never before written a daily story. Great colleagues in both Washington and Boston made it an exceptional place to practice journalism: Matt Viser, Bryan Bender, Farah Stockman, Susan Milligan, Scott Helman, Michael Kranish, Michael Levenson, Marcella Bombardieri, Jim Smith, Foon Rhee, Gareth Cook, and Steve Heuser. Thanks to Christopher Rowland for letting me remain part of the family, and to Stephanie Vallejo for all her help and good humor along the way. I am also in hock to the transatlantic gang at Monocle for harboring this refugee from the American newspaper crisis, and their understanding when I felt moved on short notice to write this book: Tyler Brûlé, Andrew Tuck, Aisha Speirs, and Steve Bloomfield.

This book started as an article for The New York Times Magazine about the use of behaviorally minded field experiments in politics. I lived with the piece for nearly a year, and on several occasions I worried that I had lost the access and cooperation of subjects I would need to breach the secretive world where the most compelling and influential research was taking place. At one point, fearing that I wouldn’t be able to deliver the narrative I had promised, I wrote my editor, Chris Suellentrop, to suggest we just abandon the assignment. “It’s too good of a story to give up without a little fight,” he wrote back. Chris was right, and I owe him for his commitment to telling that story—along with Gerry Mazorzati for commissioning it, Hugo Lindgren for publishing it, Lia Miller for fact-checking it, and James Ryerson for carrying it across the finish line. Thanks, as well, to David Haskell and David Wallace-Wells at New York for further indulging my interest in the science of politics. Since then, I have joined Slate to cover that terrain on an ongoing basis, and have been part of the best political team on the Web, including David Plotz, Michael Newman, Will Dobson, John Dickerson, Dave Weigel, and John Swansburg, who edits better than anybody who can edit faster, and edits faster than anybody who can edit better.

The greatest debt is owed to those whose names fill this text. My subjects and sources are often those who, in an industry propelled by self-promotion, choose to remain in the background. But this book is possible only because they shared my commitment to having the story of the largely underappreciated revolution in American politics be told with the scope and detail the subject demands. Over the course of the year I reported and wrote this book, I conducted hundreds of interviews, and the identities of those who shared their time and candor with me will be apparent to readers. (Nearly all of my interview subjects spoke, to some extent or another, on the record.) I am most appreciative of their patience. I began this project with little grasp of even the most basic technical aspects of randomized experimentation or statistical modeling, and when I think back to some of my earliest interviews I am embarrassed by some of the questions I asked and can only imagine how weary they made my interlocutors. There are a few whose contributions—unearthing documents, tracking down other sources, making introductions—are out of proportion to whatever place (if any) they have in the narrative: Debra DeShong Reed, Anu Rangappa, Amy Chapman, Brent Colburn, Mark McKinnon, Adrian Gray, and Regina Schwartz.

A salute is due to traveling companions from an epic 2008 campaign and electioneering adventures since: Bret Hovell, Adam Aigner-Treworgy, Bethany Thomas Jordan, Mosheh Oinounou, Kelly O’Donnell, Michael Cooper, Elisabeth Bumiller, Lisa Lerer, Maeve Reston, Katie Connolly, Seema Mehta, Athena Jones, Jonathan Alter, Hans Nichols. Former colleagues RoseMarie Terenzio and Lisa Dallos remain good friends who have offered a useful boost as I’ve tried to find my footing writing books. I can thank a warm circle of erstwhile Washingtonians for welcoming me to Washington: Mike Madden, Mindy Saraco, Mark Paustenbach, Dan Reilly, Meg Reilly, Scott Mulhauser, Cecily Craighill, Betsy Barnett, Ben Wallace-Wells, Juliet Eilperin, Jill Zuckman, Carrie Budoff Brown, Jose Antonio Vargas, Christina Bellantoni, Brian Weiss and Aimee Agresti, Michael Schaffer, Keltie Hawkins, and Eleanor and Eva Schaffer. Good friends still make Philadelphia feel in many ways like home: Jason Fagone, Rich Rys, Andy Putz, Michael Karloutsos, Phil Press, Russ Tisinger, Jeff Steinberg, Bridget Morris, Alessandra Bullen, Elliot Bullen.

Some of my best friends happen to be talented writers and editors who offered their time to read and work over my text at various stages: Lisa Wangsness, Benjamin Wallace, Jack Bohrer, Geoff Gagnon, April White. They made essential contributions, as did others. I never had the good sense to study with Rick Valelly when I attended Swarthmore, but I’m glad to have gotten to know him since; he offered sage scholarly counsel on this project, partially by belatedly assigning me the political science syllabus I dodged as an undergraduate. I receive continued inspiration from Jonathan Martin; he is probably the best political reporter of my generation, and I feel fortunate to have the opportunity to watch him up close as he practices his craft. And above all there is my longtime friend and professional coconspirator, James Burnett, who makes just about all my work better.

A young writer could not have better champions than my agent Larry Weissman and his partner, Sascha Alper. I knew Larry had led me into the right hands for this project when at one of our early meetings my new editor, Zachary Wagman, asked me—more than eighteen months before election day—what I thought of Martin Heinrich’s chances in New Mexico’s Democratic Senate primary. He was responsible for publishing an ebook preview from this work, Rick Perry and His Eggheads, a remarkable midsummer feat of improvisation and nimbleness. For its success I owe thanks to the rest of the team at Crown: Annsley Rosner, Dyana Messina, Rachel Rokicki, Julie Cepler, Michael Gentile, and Molly Stern. I am fortunate to have as talented a journalist as Dan Fromson fact-checking my manuscript (along with timely research assistance from Claire Kim) and as creative a tactician as Mary Krause making sure the final product finds an audience. Thanks to David Fields for once again agreeing to briefly unretire from photography to take my portrait for the book’s jacket, to Dan Shepelavy for his aesthetic guardianship, and to Tom Kennedy and Dan Seng at Tom Kennedy Design for their work on the book’s website.

My family let me knock on strangers’ doors and spend school nights at phone banks as I dabbled in political campaigns beginning at the age of twelve and similarly encouraged me when I settled into another line of work that polls show to be one of the country’s least admired. For that support and love I thank my grandmothers, Olga Issenberg and Pola Brodzki; my late grandfathers, David Issenberg and Ludwik Brodzki; my aunt Gayle Brodzki; my sister, Sarina; and my parents, to whom this book is dedicated.