"Is that a Romney float or is that a Portman float or is that a friends-of-Portman float?" asks Paul Light, a professor of government at New York University. "You just don't know."
There's an easy remedy available to wanna-be contenders who've been left off the short list, says Light. All it takes is a well-placed whisper from a friend of a friend to land on the veep list.
"Instead of saying, 'I could've been a contender,' you can say, 'I am a contender' even if you're not," says Shrum.
No one's owning up, but Rep. Eric Cantor, R-Va., managed to get mentioned as a veep contender in 2008 although the notion that he was under consideration was laughable to GOP nominee John McCain's campaign.
Shrum, who worked on Massachusetts Sen. John Kerry's 2004 campaign, when John Edwards was the running mate, says then-New Mexico Gov. Bill Richardson "very much wanted to be seen as being vetted in 2004, until he pulled his own name out of contention." Shrum's theory is that Richardson never wanted to be chosen, but wanted to make a name for himself in preparation for his own 2008 run for president.
Joel Goldstein, an expert on the vice presidency at Saint Louis University School of Law, said presidential candidates may try to flatter a politician or appease a voting bloc by letting it be known that a certain person is under consideration when that person doesn't have a chance. Some call that an "ego vet."
What really matters, says Goldstein, is who's been asked by the campaign to submit documents and answer questionnaires as part of a thorough vetting process.