Romney-Christie, Gingrich-Rubio are most likely ticket pairings

·Computer Scientist

If you're curious why the candidates were tripping over themselves to out-praise Marco Rubio, Florida's Republican junior senator, at the last debate, look no further than the political market Intrade, where Rubio is in first place to be second fiddle with a 24 percent chance of being the eventual winner's running mate. (Meanwhile Joe Biden is the overwhelming favorite to remain Obama's choice.)

But who gets the would-be VP nod depends greatly on who is the nominee. As Newt Gingrich's odds of winning have spiked and dissipated twice in the last two months, the market for vice presidential candidates has reacted. Because the movement happened over a fairly short time period -- I analyzed the past 90 days -- and because not much else seems to have occurred to impact the veepstakes picture during that time, we can guess that most of the changes in the VP market are driven by the shifting fates of Romney and Gingrich at the top. With this assumption, we can compute estimates of which pairings are most likely.

If Mitt Romney is the Republican nominee, my model estimates that he is 25 percent likely to pick Chris Christie as his running mate, a popular moderate governor from New Jersey who himself flirted with running for president before strongly endorsing Romney. (This in spite of the fact that you'd have two Northeasterners on the ticket.) The market puts Christie's overall chance of being the VP of any Republican nominee at only 14 percent, but because his odds tend to rise in tandem with Romney's, my model boosts his chances to 25 percent in the scenario where Romney is the nominee. Rubio is a close second to be Romney's right-hand man at 22 percent. Rubio's VP odds actually drop whenever Romney's go up (they are anti-correlated), but because Rubio's such a likely overall pick, he's still the second-most likely Romney pairing. Rubio so far hasn't endorsed a presidential candidate and has repeatedly said he's not interested in the VP job. No other candidate rises above single digits as Mitt's pick for a-heartbeat-away.

If Gingrich wins the Republican primary, he's most likely, at 30 percent, to pair up with Rubio. Christie virtually falls out of the running for VP at below 5 percent if Gingrich emerges the primary winner. Over the past 90 days, when Gingrich rose in the presidential market, Rubio tended to rise too and Christie tended to fall in the vice presidential market.

These estimates are based solely on data unaided--and untainted--by political intuition. Using a technical analysis called logistic regression, I extrapolated to the point of a Gingrich win to derive an estimate for Rubio's chances in that scenario. I did the same for all pairs of Republican presidential and vice presidential candidates. It's important to note that what we are measuring here is a statistical correspondence, and an extrapolated one at that, not a proven cause-effect relationship.

Interestingly, Rubio is not the VP candidate with the highest correlation with Gingrich: Romney is! Still, the chance that Gingrich would pick Romney as his running mate is only 7 percent. That's because Romney is an unlikely VP pick overall. Also, Romney as the nominee is extremely anti-correlated with Romney-as-veep, a sanity check suggesting the market and the model are producing sensible results. (As much as Romney might like, you can't choose yourself as your vice president.) Extrapolating from the co-movements of different markets isn't perfect, but it's the best we can do in the absence of true combinatorial prediction markets.

Of the other two Republican primary candidates, Rick Santorum is the more likely vice-presidential candidate at 5.2 percent. Ron Paul, frequently mentioned by his supporters as an ideal vice-presidential candidate, is considered negligibly likely. Yet, his son, Rand Paul, is given about 1.5 percent likelihood of being the Republican VP candidate. Below is a list of candidates compiled from Intrade.



Marco Rubio

24.2 %

Chris Christie

13.2 %

Bob McDonnell

7.2 %

Susana Martinez

6.8 %

Rob Portman

4.8 %

Paul Ryan

4.3 %

Rick Santorum

4.1 %

John Thune

3.9 %

Mitch Daniels

2.7 %

Condoleezza Rice

2.5 %

Bobby Jindal

2.5 %

Brian Sandoval

1.9 %

Nikki Haley

1.8 %

Rand Paul

1.5 %

Tim Pawlenty

1.5 %

Mike Huckabee

1.3 %

Newt Gingrich

1.1 %

In addition, the following candidates have a less than 1 in 100 chance according to Intrade: Jim DeMint, Jeb Bush, Jon Huntsman, Mitt Romney, Gary Johnson, Allen West, Kelly Ayotte, John Kasich, Sarah Palin, Rick Perry, Rudy Giuliani, Michele Bachmann, Herman Cain, Michael Bloomberg, David Petraeus, Pat Toomey, Eric Cantor, Mike Pence, JC Watts, John Kasich, Judd Gregg, George Pataki, Scott Brown, Haley Barbour, John Bolton, Dave Heineman, Meg Whitman, Carly Fiorina, Donald Trump , Bill McCollum, John Boehner, and Buddy Roemer.

Follow the real-time numbers on Intrade or PredictWise.

David Pennock is a Principal Research Scientist at Yahoo! Research. Follow him on twitter @pennockd.

Chris Wilson contributed.

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