Romney didn’t see it that way, at least not at the start. When he tapped longtime adviser and confidante Beth Myers to lead the search for his VP, Mitt put forth two criteria and a precept. The criteria applied to the candidates: that they be qualified and immediately perceived as qualified to be Commander in Chief, and that there be nothing in their background that could become a distraction for the campaign. The precept applied to Myers and her assignment. When decision time came, Romney said, he wanted to have a choice—not be informed, with the clock ticking, that there was really only one viable option.

Myers set up her operation in a third-floor office on Boston’s Commercial Street that became known as “the clean room.” Because the Romney campaign’s servers were under continual assault by Chinese hackers, the computers in the clean room were not connected to the Internet. Myers insisted that the team be extremely cautious about what they put in e-mail when using their regular computers. Ted Newton and Chris Oman, two veep background checkers, concluded it was best to communicate in code. Based on their junk-food-saturated vetting diet, they called their undertaking Project Goldfish (after the crackers)—ultimately giving each of the VP finalists an aquatic code name. Myers’ plan was to have Project Goldfish completed by Memorial Day. In April she presented Romney with a list of two dozen names, which he whittled down to 11: Kelly Ayotte, John Cornyn, Chris Christie, Mitch Daniels, Bill Frist, Mike Huckabee, Bob McDonnell, Tim Pawlenty, Rob Portman, Marco Rubio and Paul Ryan.

Within a month, the vetters had assembled preliminary research books on the 11, which Romney perused and then rendered his short list: Christie (Pufferfish), Pawlenty (Lakefish), Portman (Filet o Fish), Rubio (Pescado) and Ryan (Fishconsin).

In the nine months since Christie’s endorsement of Romney in October 2011, Boston had formed a mixed view of the governor who George W. Bush had once nicknamed Big Boy. Christopher James Christie, 51, was less than two years into his first term as governor of New Jersey, suave as sand­paper and morbidly obese. He was also one of the most intriguing figures in American politics. His voice was like an air horn, cutting through the clutter. There was no one better at making the referendum case against Obama, at nailing the President to the wall with ferocity and caustic humor. Christie’s temperament was ideally suited to the unfolding tenor of the race. “We’re in a street fight, and he’s a street fighter,” Romney’s chief strategist Stuart Stevens told Romney. “He’s the best street fighter—and he’s comfortable saying things that you’re not comfortable saying.”

He was also a fundraising dynamo, but he and his staff were overbearing and hard to work with, demanding in ways that would have been unthinkable from any other surrogate. Months earlier, Christie had banned Romney from raising money in New Jersey until Christie had given the O.K. to do so—a move Romney found galling, like something out of The Sopranos. Are you kidding me, Mitt thought. He’s going to do that? There were plenty of New Jersey donors who’d given money to Mitt in 2008; now Christie was trying to impose a gag order on talking to them?  “He sounds like the biggest asshole in the world,” Stevens griped to his partner, Russ Shriefer. More recently, Trenton insisted on private jets, lavish spreads of food, space for a massive entourage. Romney ally Wayne Berman looked at the bubble around Christie and thought, He’s not the President of the United States, you know.

Chronically behind schedule, Christie made a habit of showing up late to Romney fundraising events. In May he was so tardy to a donor reception at the Grand Hyatt New York that Mitt wound up taking the stage to speak before Christie arrived. When the Jersey governor finally made his grand entrance, it was as if Mitt had been his warm-up act.

Punctuality mattered to Romney. Christie’s lateness bugged him. Mitt also cared about fitness and was prone to poke fun at those who didn’t. (“Oh, there’s your date for tonight,” he would say to male members of his traveling crew when they spied a chunky lady on the street.) Romney marveled at Christie’s girth, his difficulties in making his way down the narrow aisle of the campaign bus. Watching a video of Christie without his suit jacket on, Romney cackled to his aides, “Guys! Look at that!”

But Mitt was grateful for Christie’s endorsement and everything else he’d done. He appreciated Chris’ persona, his shtick, his forcefulness, his intuitive connection with voters. That night at the Grand Hyatt, at a high-dollar dinner after the main event, Christie’s argument for Mitt was more compelling than anything the nominee could manage.

The list of questions Myers and her team had for Christie was extensive and troubling. More than once, Myers reported back that Trenton’s response was, in effect, Why do we need to give you that piece of information? Myers told her team, We have to assume if they’re not answering, it’s because the answer is bad.

The vetters were stunned by the garish controversies lurking in the shadows of his record. There was a 2010 Department of Justice inspector general’s investigation of Christie’s spending patterns in his job prior to the governorship, which criticized him for being “the U.S. attorney who most often exceeded the government [travel expense] rate without adequate justification” and for offering “insufficient, inaccurate, or no justification” for stays at swank hotels like the Four Seasons. There was the fact that Christie worked as a lobbyist on behalf of the Securities Industry Association at a time when Bernie Madoff was a senior SIA official—and sought an exemption from New Jersey’s Consumer Fraud Act. There was Christie’s decision to steer hefty government contracts to donors and political allies like former Attorney General John Ashcroft, which sparked a congressional hearing. There was a defamation lawsuit brought against Christie arising out of his successful 1994 run to oust an incumbent in a local Garden State race. Then there was Todd Christie, the Governor’s brother, who in 2008 agreed to a settlement of civil charges by the Securities and Exchange Commission in which he acknowledged making “hundreds of trades in which customers had been systematically overcharged.” (Todd also oversaw a family foundation whose activities and purpose raised eyebrows among the vetters.) And all that was on top of a litany of glaring matters that sparked concern on Myers’ team: Christie’s other lobbying clients, his investments overseas, the YouTube clips that helped make him a star but might call into doubt his presidential temperament, and the status of his health.

Ted Newton, managing Project Goldfish under Myers, had come into the vet liking Christie for his brashness and straight talk. Now, surveying the sum and substance of what the team was finding, Newton told his colleagues, If Christie had been in the nomination fight against us, we would have destroyed him—he wouldn’t be able to run for governor again. When you look below the surface, Newton said, it’s not pretty.

Early Sunday morning, July 15, Romney got on a conference call with the Boston brain trust to talk about the veepstakes.

The overwhelming consensus was for Ryan. He was young, telegenic, Irish Catholic, with blue collar appeal, and he might put his state in play. He would rouse the base and sharpen the policy contrast with Obama. While the Ryan budget and Medicare plan were political cons, Romney was half pregnant with them anyway—so why not marry their most articulate defender? Two of Mitt’s closest confidants, former Utah Governor Mike Leavitt and his former business partner Bob White argued that Mitt should pick the best governing partner; privately, both expressed support for Ryan. Look, Mitt, you’ve never worked in Washington, Leavitt said. Having someone who can swing a bat for you on the Hill and knows the budget inside out makes a lot of sense.

But Stevens remained unconvinced about Ryan and adamantly in favor of Christie. Shielded from the crash vet and what it was turning up, Romney’s chief strategist was making a purely political argument—one that contradicted the considered judgment of virtually everyone else on whom Mitt relied for advice. Such was the potency of the Romney-Stevens bond that Mitt kept Christie in the pack.

Romney was somewhat shielded from the Pufferfish vet too, but he knew it wasn’t going smoothly. Myers informed him that a significant problem had not been solved: the severe limits on political donations from the financial community that would have applied to a Romney-Christie ticket under New Jersey’s strict pay-to-play regulations which limited the amounts potential donors employed by financial services firms who did business with the state could contribute.

Romney’s lawyers were still looking into the matter. Facing Obama’s formidable fundraising machine, it appeared that picking Christie could cost Romney a serious chunk of change. One possibility was that if Christie were picked as VP, Romney would no longer be able to raise money from many financial institutions for the rest of the campaign. Not great, but manageable, maybe. Another possibility was that Boston would have to return the cash it had already raised on the Street—­unacceptable. The attorneys had been exploring workarounds; none were watertight.

The easiest solution would be for Christie to resign as governor if he got the nod. A few hours after the conference call, Romney phoned him to float that notion. “Are there any circumstances in which you’d consider resigning to become the nominee?” Mitt asked.

Christie asked for time to think it over.

Romney said that his lawyers were still working on the pay-to-play conundrum.

“Why don’t you talk to your counsel and see what happens?” Christie said.

Romney hung up the phone convinced by Christie’s reaction that resignation was not in the cards. (He was correct.) “Look, let’s find out if we can get an answer” on pay-to-play, he told Myers. But let’s keep pushing on the vet—and pushing on Trenton.

Four nights later, on July 19, Myers’ team put the finishing touches on the Pufferfish vetting dossier. Included was a DVD with some of Christie’s most outlandish or unnerving YouTube hits: his castigating a pro-gay-marriage New Jersey assemblyman as “numb nuts,” his angrily berating a constituent while chasing him down the Seaside Heights boardwalk, brandishing an ice cream cone. But the main event was the 35-page written report titled “Chris Christie memo 71912 FINAL.”

After 11 days of teeth-gnashing labor, several of the issues that the vetters had unearthed around Christie were still unresolved. Myers and her team were sticklers. Uncomfortable producing a final report they considered incomplete, they made a point of being meticulous about framing and flagging the problems, including a refrain in bold applied to a number of items.

On Todd Christie’s securities-fraud settlement: “[Governor] Christie has been asked to disclose whether Todd Christie incurred any monetary or other penalty as a result of the SEC/NYSE action. If Christie’s possible selection is to move forward, this item should be obtained.” On Christie’s defamation lawsuit: “Christie has been asked to provide the terms of the settlement of this matter. If Christie’s possible selection is to move forward, this item should be obtained.” On Christie’s household help: “Christie has been asked to provide the names and documented status of all domestic employees. This material has not been received. If Christie’s possible selection is to move forward, these items should be obtained.” On Christie’s lobbying clients: “Christie has provided only one of the twelve or so [public disclosure] filings made [in the time he was a lobbyist] … If Christie’s possible selection is to move forward, these items should be obtained.”

Then there was this: “In response to the questionnaire, Governor Christie indicates that he has no health issues that would hinder him from serving as the vice-presidential nominee. Published reports indicate that Christie suffers from asthma and was briefly hospitalized last year after he suffered an asthma attack. He is also obese and has indicated that he struggles with his weight. ‘The weight exacerbates everything,’ he is quoted as saying. Christie has been asked to provide a detailed medical report. Christie has been asked to provide a copy of all medical records from his most recent physical examination. If Christie’s possible selection is to move forward, this item should be obtained.”

Despite the language in the report indicating that Christie had not been sufficiently forthcoming with his medical records, Romney and Myers agreed that what he had provided put their minds at ease about his health. But the dossier on the Garden State governor’s background was littered with potential land mines. Between that and the pay-to play snag, there was no point in thinking about Christie further. With the clock running out, Romney pulled the plug again, this time for good.

Mitt meditated on the choice that now seemed inevitable: Ryan. Beyond all the political pros and cons, Romney felt comfortable with Paul. He reminded Mitt of junior partners he used to work with at Bain: eager, earnest, solicitous, smart and not at all threatening. Bob White had a phrase for these buttoned-down go-getters, which he applied to Ryan: “client-ready.”

On the flight home from his July trip to England, Israel and Poland, Romney inhaled a long profile of Ryan in the New Yorker, which traced the Congressman’s ascendancy to the position of de facto intellectual and ideological leader of the GOP. Impressed by what he read, he gave the piece to Stevens, who paged through it on the plane too. What do you think now? Romney asked.

“I can’t tell you who to fall in love with,” Stevens said with a shrug.

The campaign’s high command held a 45-minute impromptu meeting in Myers’ office the day after Romney returned home. With Christie out of the picture, Stevens switched to making the case for Portman. Romney remained mum about which way he was leaning.

When the meeting was over, he stayed behind with Myers. In five days, she noted, a so-called protective pool of reporters would start accompanying him at all times, making it difficult to orchestrate the kind of secret maneuvers that a vice presidential unveiling entailed. Unless we want to get real cloak and dagger, you should probably make up your mind pretty soon, Myers said.

“Oh, O.K.,” Romney said. “Then I’ve made my choice—I’ll pick Paul Ryan.”

Romney called Ryan and asked him to come to Boston for a sit-down.

Ryan hung up the phone, stunned. Are we ready? he asked his wife Janna. I think this is it.

Ten days later, it was.

Obama was en route from the White House to his Chicago headquarters when the Romney-Ryan ticket debuted on the deck of the U.S.S. Wisconsin in Norfolk, Va., on Saturday, Aug. 11. He was surprised by the Ryan pick, couldn’t fathom the political calculation that led Mitt to choose the front man for a set of policies that were so broadly unpopular.

I don’t get it, Obama said to senior adviser David Plouffe and communications director Dan Pfeiffer. Why is he doubling down?

When the President arrived at Chicago HQ, he greeted the troops and settled in for a presentation from campaign manager Jim Messina. The campaign manager addressed the Ryan pick and, more broadly, the state of the race on the eve of the conventions.

The Obamans polled and focus-grouped extensively on Romney’s veep options in order to be ready to respond. Their research showed that Tim Pawlenty’s “pro-beer, pro-hockey” persona might have helped ameliorate the nominee’s case of affluenza. The second best pick was Portman, who would have given Romney a small but significant bump in Ohio.

Putting Ryan on the ticket, by contrast, did nothing good for Romney, in Chicago’s view.

Not only did his presence highlight Medicare and the budget, where the Obamans believed that they were playing the winning hand, but it would let them twin up Romney with the terminally unpopular congressional wing of the GOP. It also seemed to represent a bedrock strategic surrender. For more than a year, Boston had doggedly pursued Stevens’ vision of the race as a referendum, trying to keep the focus on Obama’s economic mismanagement, high unemployment and moribund GDP growth.

The elevation of Ryan seemed to signal a sharp U-turn, highlighting the issues of deficits, entitlements and taxes—and, in so doing, accepting Chicago’s framing of the election as a choice.