The media race to find out the answer is nearly as strenuous and exciting as the search itself.
In the days leading up to the announcement, which traditionally comes shortly before the nominating conventions, reporters routinely stake out the homes of the would-be VP choices. And the nominees go to great lengths to keep everything a secret as long as possible.
In 2012, the press gathering outside Rep. Paul Ryan's Wisconsin home prompted him to escape out his backdoor
through a forest to avoid being detected. A Mitt Romney aide arranged to secretly meet him on a back road when he emerged from the wooded thicket. Ryan's great escape was a success.
Despite the many evasive maneuvers at their disposal, the Internet has given reporters -- and anyone who wants to play along too -- tools to craftily detect unorthodox movements around the country. Keep a close eye on websites like Flight Aware
, which logs every plane in the sky and tracks its progress across the country. Private jets flying from a small airport where one of the potential VP picks lives to a presidential campaign's headquarters always set off alarm bells.
In 2008, a keen-eyed observer may have noticed that a private plane had been dispatched from Anchorage, Alaska, heading to Flagstaff, Arizona, a city near Sedona, where then-Republican presidential nominee John McCain owns a home. The plane then flew on to Middletown, Ohio, where McCain was set to make his announcement. Around the same time, another private plane flew directly between Anchorage and Middletown, which was loaded with the rest of Palin's family. All of this was accomplished without the mainstream media picking up on it, although some bloggers connected the dots together before the announcement.
The investigation process is a lot simpler when potential veeps have their own plane, allowing veep hunters to keep a close eye on the jet's tail numbers. Of course, campaigns already know that this could be a dead give-away, so they could easily hitch a ride on a friend's plane to avoid detection.
But unlike past Republicans, Donald Trump hasn't made his search as much of a secret.
He has openly named his favorite choices, including Indiana Gov. Mike Pence, New Jersey Gov. Chris Christie and former House Speaker Newt Gingrich. Trump and his family joined Pence for a meeting at the governor's mansion in Indianapolis on Wednesday -- they entered through the front door! -- and Trump spoke with Christie on the phone as well. Of course, these public displays of affection could just be an elaborate ruse to divert attention from the real contenders.
But like most of Trump's campaign, his search for a second fiddle is mired by unconventional circumstances. While most prominent politicians normally say they'd be honored to be chosen, many Republicans have made clear they want no part in Trump's administration. So Trump's pool of potentials is relatively limited.
Even choosing among opponents he vanquished during the primaries — which President Barack Obama did when he picked Joe Biden -- would be a tough sell, given the terrible things they have said about them. Take Marco Rubio, who called Trump a "con artist" and "the most vulgar person ever to aspire to the presidency." Or Ted Cruz, who finds Trump "utterly immoral" and considers him a "pathological liar." Jeb Bush believes he's "not qualified to be president" and Lindsey Graham thinks he's a "race-baiting, xenophobic, religious bigot." So, yeah, it's fair to say they won't be returning calls from Trump's VP search team, should they even pick up the phone at all anyway.
Hillary Clinton's VP search, meanwhile, has elicited less excitement, but has been equally mysterious nonetheless.
She took a day off from campaigning last week to examine the research books provided by her campaign staff that details each potential contender's positives and negatives, deeds and misdeeds. It's not uncommon for presidential campaigns to undergo full-scale investigations into the private lives of their hopefuls, in hopes of avoiding any embarrassing indiscretions or sordid details. These searches range from everything involving public voting records to whether they have any "dead girl or a live boy," skeletons, to paraphrase former Louisiana Governor Edwin Edwards.
In the end, despite all the cloak-and-dagger tactics, the intrigue and the vast resources news organizations devote to this game, the result will be inevitable: Each candidate will pick somebody. Until then, we'll keep eying the skies and listening for runners in the forest.