Barack Obama appears with his selection for vice president, Sen. Joe Biden, in 2008. (Linda Davidson/The Washington Post)

For months, we've debated and analyzed and marvelled at the 22 people who at one time were considered real(ish) contenders for the presidency. Some 45 million people have already weighed in, helping shrink the field down to five (or two, depending on whom you ask) — a seeming validation of the laborious process that demands each state savor the candidates like a political gourmand before reaching a conclusion.

Here, toward the home stretch of this thing, it's easy to forget that this isn't the only path to the presidency. That a guy became president in 1974, for example, simply by virtue of being in the right place at the right time. Gerald Ford was plucked from the House to be Richard Nixon's vice president, a job he held for about nine months, until his promotion. The only election he won to get there was besting Jean McKee in the 1972 race for Michigan's 6th Congressional District. The 118,027 people who voted for Ford that year had no idea that they were, in effect, choosing the next president.

That, in a nutshell, is what makes the vice presidency so bizarre. Nixon could have picked anyone he wanted, and, once confirmed by Congress, left that person in control of the United States. It wasn't even 118,027 people that elected Ford. It was 479 people, 387 of whom worked alongside Ford in the House. Those 479 people — 0.001 percent of those who've voted so far — chose the next president.

Even under non-bizarre circumstances, choosing a vice president is an unusual part of the process.

"It's a very peculiar arrangement," former White House counsel Bob Bauer told us when we spoke with him by phone on Thursday. "A person decides to take another person to be vice president of the United States. And all of the resources that are required for evaluating the choice and then proceeding with it are privately deployed." All of the money and consideration and effort that goes into the presidential understudy happens quietly and according to the whims of only one person: the nominee.

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Or, sometimes, just a candidate. Ted Cruz's announcement this week that he had selected Carly Fiorina to be his running mate (on the off-chance that he earns the chance to run) contained a lot of oddities, including that it was a bit presumptuous. But it was also strange because it was so early.

Bauer was co-chairman of an effort by the Bipartisan Policy Center to draft a set of recommendations for the vice-presidential vetting process. As part of that, the group created a chart showing when vice presidents had been announced relative to the flow of a campaign. Normally, it's shortly before the convention, allowing for time to both win the nomination and thoroughly vet someone. Cruz skipped the former by so much that one can reasonably question how well he did the latter.

The Bipartisan Policy Center report figures that you should allow for about two months, at a minimum, for a thorough vetting process (which would require Cruz's efforts on Fiorina to have begun about two weeks after she dropped out). Why so long? Because uncovering every minute detail you could ever want to know about someone else takes a bit of time.

"Think college application," Stuart Stevens, who worked with the campaign of then-Gov. George W. Bush in 2000 and Mitt Romney in 2012, said when we spoke by phone. Potential vice presidential candidates are asked for a broad range of information: tax records, voting records, public records (if they've held office), medical records, histories of divorce or child custody battles. It's everything, Stevens said, except a personal essay — though the process also includes any number of interviews, too.

The process is so grueling that there's a critical step before the application: The potential candidate has to agree to undergo it. This isn't a no-brainer. It involves a lot of time, energy and expense. It's not just the potential candidate's time, either. Accountants that prepared tax documents are looped in, as can be doctors and people who have worked with the candidate in the past. And it goes outward from there.

"Nowadays you might need specialized support for Web searching, social media searching," Bauer said. "That may bring in family members — children and uncles and aunts — who are may be posting with the same last name, or easily identified, controversial material on the Web. That's got to be picked up and evaluated." The tweet that brought down the president.

There's no standard set of questions or concerns that are addressed. That's all up to the candidate. What disqualifies a candidate? "For some, being involved in four bankruptcies might be disqualifying," said Stevens (who is not a Trump supporter). "There was a time when admitting to illegal drug use would have been disqualifying. Now it seems practically mandatory." Things evolve. Different people look for different things.

One key factor is how the two candidates will work together. "Ultimately, the best vice presidential choices are governing choices," Stevens said. "Because ultimately, it's a governing role, and they certainly can have much more impact on governing than campaigning." Stevens's advice to a presidential candidate? If you had all of the potential candidates in a room while you were trying to make a difficult decision, and you could only ask one of the people in that room for advice, whom would you pick?

Figuring out who you would work well with is, of course, tricky. Part of it means coming to agreement on where the candidates do (and don't) disagree on policy. (In 1980, George H. W. Bush was asked about his critiques of Ronald Reagan's economic policies on the trail and famously replied, "God, I wish I hadn't said that.") Part of it comes from interviews with past colleagues. Part of it, clearly, is instinctual.

The Bipartisan Policy Center report notes a way that Mitt Romney got to know candidates in 2012: He made campaign appearances with them in their home states. The stops "were essential opportunities during which Romney could judge the candidates’ qualities and assess the factor of personal chemistry that will determine the success of the relationship on the campaign trail or in the government," the report suggests.

That said, it's worth circling back to Stevens's comment that a vice presidential pick is more useful for governing than campaigning. Vice presidents have historically not done much to help bring in electoral votes, and Stevens is skeptical that it's even worth polling on them. Who, after all, would have had a strong opinion on the bare-bones portrait of Sarah Palin that a pollster could have asked about?

There are three points at which the VP pick significantly influences the campaign, in Stevens's estimation: During the rollout, at the convention and during the debate. Not that the campaigning is entirely unimportant; it, too, requires that campaign and potential vice president be on the same page. If you don't want to spend weeks barnstorming mid-sized cities in Ohio and North Carolina, the job may not be for you.

All of this vetting is run separately from the main campaign operation. There's generally a separate operation established with an identified lead or leads, the people responsible for gathering and processing all of the information. (In 2000, famously, the lead was Dick Cheney, the eventual choice.) Once a group of potential candidates has been identified — say, five to seven potential people — that lawyer-heavy group collects the information, conducts interviews with relevant individuals, and ultimately reports back to the candidate. (Parts of that report are often given orally, given that so much sensitive information is being conveyed.) At the end of the day, of course, the final decision is the candidate's.

In Stevens's experience, candidates aren't terribly interested in outside opinions about the names that are included. He told a story about jogging with then-Gov. Bush near Crawford, Tex., in 2000. Stevens had an idea of who he thought might be a good vice president, and asked Bush if it was a good time to bring it up. "Hell no," Bush replied, good-naturedly. "Why should I give a damn what you think?"

Later, Bush put a finer point on it. "Stevens, let me give you a tip," he said. "When a guy's getting married, it's better to wait for the guy to ask you about the chick before you volunteer."

With the recent exception of Gerald Ford, America generally gets some say in who the vice president is, by virtue of the campaign process. But that's after the fact. For all of the nonsense that's gone on over the past 16 months, for all of the people we've discussed and dissected and watched fade away, the president after the president after Barack Obama could end up being someone who, right now, lawyers in a conference room in Brooklyn or Manhattan are adding to the bottom of a very private list.