AUSTIN -- It may sound like a bizarre way to gauge a political contest, but history shows gamblers long served as political bellwethers before the advent of scientific polling in the early 20th Century, with the latest odds carried in newspapers in much the same way as the polls of today.
With the Republican presidential nomination all but sewn up, who Mitt Romney will pick as his 2012 running mate is still anyone's guess. Of course in Las Vegas, guessing is big business, and the nation's largest online betting website, Bovada, has published odds on 20 choices for the vice presidential slot.
"I'd say 2008, the general election, there was kind of the tipping point for us in regards to garnering a lot of this online interest in wagering on politics," said Bovada head oddsmaker Pat Morrow. "It used to just be that we'd have which party would win the election -- a pretty straight cut wager, Democrats or Republicans, but due to the overwhelming interest, we have been adding these additional props each year."
So who's number one?
Despite countless dismissals of any interest in the vice presidency, Florida Senator Marco Rubio leads the pack at 2/1 odds.
"He has a lot of things that Romney needs," said Morrow. "He's charismatic. He's young. He's considered the champion of the Tea Party, the crowned prince of the Tea Party. He's also Cuban-American, so that helps Romney with Latino votes."
"It's that kind of thinking," Morrow explained about the oddsmaking process. "We do watch our fair share of CNN, ABC, and we follow the polls as much as everyone else, but for stuff like this, we have to just go a little bit deeper."
So just what goes into choosing a running mate from a candidate's point of view?
University of Texas professor of history and government Jeremi Suri says candidates should ask themselves three questions. "Will the person provide me with electoral votes in states where I might not as a presidential candidate be as secure?" said Suri. "Second, will this person make me look better? Will they not overshadow me? Will they provide certain attributes that I might not have -- charisma in certain environments, attraction to certain ethnic groups? Then third, will this person work together with me as a team?"
For Romney, Suri says the key will be finding a partner with the right balance of conservative appeal and the ability to reel in support from a fractured Republican base.
"He is going to run himself after the Independents, and he is going to want someone to his right as his running mate," Suri explained. "So someone who can connect with Southern voters, someone who can connect with religious voters, and someone who's seen as a little more of a reliable fiscal conservative. He's going to look for someone who has some charisma, but not too much charisma because he doesn't want to look as if he's vanilla next to the more interesting candidate he's running with."
Many believe Sen. Rob Portman may just fit the bill. The junior senator from swing state Ohio is the insiders' pick for the vice presidential slot, listed on Bovada at 3/1 odds.
Not far behind are New Jersey Governor Chris Christie and Wisconsin Rep. Paul Ryan, both at 9/1 odds. Rick Santorum lands at 18/1, with Sen. John McCain's 2008 Republican running mate Sarah Palin a long shot at 50/1 odds.
Suri suggests the controversy surrounding Palin may have Republicans more concerned than ever that Romney choose a known quantity as his running mate -- a concern that works against younger, untested candidates like Sen. Rubio.
"The last thing he wants is another controversy. So what I think he'll look for will be a candidate who is popular, a candidate who brings something to the ticket, but also someone who doesn't inspire another round of questions about whether Romney should be the leader of the Republican party." said Suri, adding Romney isn't likely to pick one of his former primary rivals either.
"I think he's hesitant to go toward those he's run against in the primaries, first of all, because they've said very damaging things about him, and by making one of them a running mate, he's legitimizing their comments," said Suri. "Second, he's afraid to be overshadowed. Most of the contenders in the Republican race were a bit more charismatic than Romney was. Romney was the establishment candidate. Santorum, Gingrich, and others were the anti-establishment candidates."
In the end, only Romney himself knows for sure.