Halperin and Heilemann try hard to pump some drama into 2012. Mitt Romney doesn’t just wake up some morning after sleeping badly. “The morning light shone harshly on Romney’s fitful reverie.” When the former governor Jon Huntsman (“the Utahan” to you) enters the race, it’s “Mormon rivals” on a collision course “with all the drama that implies.” Which unfortunately is not much. “But then came a bolt from the blue: a new . . . survey . . . that put him at 10 percent.” This is Santorum in Iowa, and getting 10 percent of the vote in the Iowa caucuses is not exactly what you could call a mandate to govern. But Halperin and Heilemann might.

The authors also recreate some memorable moments. There is Representative Michele Bachmann, performing a reverse Sally Field after coming in last in the Iowa caucuses, sobbing “God, I’m a loser. . . . God, I turn people off.” There is the president of the United States dropping the F‑bomb, then surprised when others drop it even more often in his presence. And according to the authors’ sources, the Obama team did consider swapping out Joe Biden for Hillary Clinton, despite denials. Some of these scenes and conversations have been previously reported, but most are brand new, based on the authors’ cyclopean (large or vast) reporting.

The authors make an earnest attempt to squeeze a unifying theme out of the book’s title. Wherever possible, they have people “doubling down” on one thing or another. But the actual theme of the book is the same as that of most books about elections: the oft-deplored “horse race.” To make this particular horse race work, they have to exaggerate the importance of bit players like the businessman Herman Cain and the self-promoter Donald Trump, both of whom are treated as potentially serious threats.

The only really exciting part of the campaign came during the Republican primaries in the spring of 2012. And writing about this period is when Halperin and Heilemann are at their best, with lots of juicy tidbits. Week by week, each candidate except Romney took a turn as front-runner, suddenly up in the polls and the one to beat, then just as suddenly yesterday’s news. Republican voters were looking for love, going on one date after another, but finally letting their heads rule their hearts, doing the responsible thing (or so they thought) and marrying that nice rich boy their mother liked so much. They knew all along that Romney was a liar. They just had to hope he had been lying before — when he presented himself as a moderate, mainstream, business Republican — and wasn’t lying now, when he presented himself as a bona fide red-meat conservative.

Halperin and Heilemann tell it pretty straight. You cannot guess, from reading the book, whom they voted for. But you can sense their devotion to a higher creed, that of the political journalist. Two provisions of that creed stand out in particular. First, no detail is too trivial to report. Blame Politico, the newspaper about politics and its accompanying Web site (for which I used to work), for this. It has built an empire on the droppings of less-successful publications. Item 2 in the creed is respect for professionalism, however it manifests itself. Political advisers ought to know when and how to lie, cheat and steal for their candidates. That’s their job, and they should do it well. It is the journalist’s job to expose them if she can. And if we all do our jobs well, we don’t need to worry about things like, well, lying, cheating and stealing.

For example, an unmistakable cloud of contempt hangs over the authors’ telling of an idea that Joe Biden had during the campaign. Why not, said Biden, send millions of households a pamphlet about where the president stood on the issues of controversy in the campaign? “Yes, a pamphlet,” they write witheringly. “Yes, millions” of copies. But what is so obviously stupid about this idea, except that it is not the kind of thing you pay the pros to come up with?