Speculation over a GOP No. 2 has been percolating for some time and has been boiling over since Romney on Monday put longtime adviser Beth Myers in charge of the selection process.

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In this March 29, 2012 file photo, New Jersey Gov. Chris Christie speaks in Manchester, N.J. Christie is one person Mitt Romney might consider for his running mate. (AP Photo/Mel Evans, File)

While Romney insists it’s “way too early” to start talking names, that’s not stopping others.

So far, there’ve been a lot of “not me” responses, including from Sen. Marco Rubio of Florida, South Carolina Gov. Nikki Haley, New Mexico Gov. Susana Martinez and former Minnesota Gov. Tim Pawlenty.

But that’s par for the course. Joe Biden and Dick Cheney once said they had no interest in the job too.

Among those who haven’t flatly ruled it out: New Jersey Gov. Chris Christie, Rep. Paul Ryan of Wisconsin and vanquished foe Rick Santorum.

Presidential candidates often perform political as well as geographical balancing acts in picking running mates, especially Republicans. And tapping someone to his political right might help Romney — a former Massachusetts governor — win over still-wary conservative and tea-party factions.

The moderate President Gerald Ford chose more-conservative Bob Dole in 1976. Conservative Ronald Reagan swung the other way in 1980, picking moderate George H.W. Bush. When a moderating Dole was the GOP standard-bearer in 1996, he named fiscal conservative Jack Kemp. George W. Bush chose more reliably conservative Cheney. And Sen. John McCain looked to his right and picked Alaska Gov. Sarah Palin.

When Romney appeared on NBC’s Jay Leno show earlier this month, he joked that he might even pick late-night competitor David Letterman. Still, a “Top Ten” list doesn’t seem near at hand.