Washington (CNN) -- Wanted: A political attack dog ready to tear into President Barack Obama. Must play by team rules, be able to withstand the pressure of a presidential campaign and pass a rigorous vetting process.
Being qualified to be president is a definite plus.
If Mitt Romney posted a job ad for a vice presidential running mate, it might sound like this. Yet despite Romney's real VP job search being secret, several potential applicants appear to be openly vying for the job, keeping their names in the audition pool by showing how sharp their teeth really are.
Florida Sen. Marco Rubio has called the president the most "divisive" in modern history. Louisiana Gov. Bobby Jindal has said Obama is the most "incompetent." Frequent anti-Obama flame-thrower Gov. Chris Christie of New Jersey has said he can be convinced to run. Ohio Sen. Rob Portman accused the president of lacking "presidential leadership." And New Hampshire Sen. Kelly Ayotte wants to debate Vice President Joe Biden.
And they are not alone. House Budget Chairman Paul Ryan and former Minnesota Gov. Tim Pawlenty are also among the potential Romney running mates who've gone on the attack.
Publicly, all of them have denied or thrown cold water on the idea of being Romney's No. 2. But don't believe that for a second. Many think that tactic is just part of the dance.
"Look, it boils down to this: For the vast majority of the so-called 'non-candidates,' it would take them a nanosecond to say, 'Yes,'" said University of Virginia professor Larry Sabato, also director of the school's Center for Politics.
"They're not kidding anybody," Sabato said. "A run for vice president is a gamble worth taking. The payoff is potentially enormous even if you lose."
Amid the auditions, consider the qualifications: The person must be ready to be president, not overshadow Romney, help him in a region or with a group where he may struggle, not depress the conservative base and stay ready to attack, attack, attack.
Biden checks many of those boxes, helping with middle- and lower-class whites who are sour on the president. Biden also fires up the Democratic base and revels in his role as political pit bull, like he did last weekend in Ohio, drumming up support among white, middle-class workers in an area where Obama hadn't done well.
"The president likes to be kind of above the fray and doesn't really believe in anger and rage; he's very cool and unflappable," said Douglas Brinkley, presidential historian and political analyst. "But that can sometimes translate as aloof. Joe Biden provides the kind of feisty, muscular counterpart."
Romney's potential running mates know if they want to rumble, they must prove they are ready for the fight. Sen. Marco Rubio Enter Rubio. The Florida freshman senator is, arguably, the loudest Obama critic on the list. Though he's frequently said he's not interested in the No. 2 spot, his activities of late suggest he's at least trying out for the job.
For example, Romney has called the president "divisive." On Saturday at a South Carolina GOP fundraiser, Rubio took that line a step further: accusing the president of being the most divisive in modern history.
Rubio could help the presumptive nominee in the battleground state of Florida, with its critical 29 electoral votes. He could help Romney close the large Hispanic gap against the president and could shore up tea party support, since many core activists don't think Romney is a true conservative.
The downside of Rubio's resume is his lack of national experience.
"He's been in the Senate as long as (Sarah) Palin was governor," Sabato said, referring to concerns that Rubio may not be ready to be president. "And he's never been vetted in a national race. Running in a single state is nothing compared to a national race."
Gov. Bobby Jindal
Louisiana's Jindal also appears to be auditioning.
Newspapers in Alabama report that Jindal recently called Obama "the most incompetent president since Jimmy Carter."
The Louisiana governor has held to the Romney campaign line as recently as Wednesday on MSNBC, touting the candidate's education proposals on the same day that Romney gave an education speech.
In that appearance, Jindal was asked about potentially being Romney's running mate. He refused to speculate, instead going on the attack against the president. But when pressed about not explicitly denying he's interested, Jindal just smiled.
Jindal, an Indian-American conservative, could help Romney with certain ethnic minorities. He is deemed qualified, and he could help the northeastern Romney with conservatives in the South.
And yet, Sabato said, "As Jindal proved when he gave the response to the  State of the Union -- he's not a scintillating public speaker."
But the governor of New Jersey is.
Gov. Chris Christie
Christie recently said Romney "might be able to convince" him to join the ticket. Christie -- a rock star in Republican circles -- has frequently echoed Romney's campaign attacks, helped other GOP candidates and fired up the conservative base.
But Christie's apparent audition may fall flat. The governor has moderate positions on some issues, which could reinforce the notion among some that Romney is too moderate himself. Also, Christie may not be able to turn traditionally blue New Jersey red.
Another potential pitfall: "[Christie's] propensity for saying controversial things, which would land him on the front pages every two or three days, overshadowing the presidential nominee," Sabato said.
Sen. Rob Portman
Rob Portman would likely not have that problem. The Ohio freshman senator is blander and breathes less fire than some of the others. But that does not mean he can't try.
Last week at a fiscal summit, Portman accused the president of lacking "presidential leadership" during last year's deficit talks.
Portman could help Romney win Ohio's 18 electoral votes -- no Republican has ever won the White House without Ohio. He is also widely deemed as qualified.
Yet, his service as President George W. Bush's budget director and trade representative could prove problematic, giving Democrats yet another Bush-staffers-as-bogeymen storyline they deployed in 2008.
Meanwhile, what better way to audition as a running mate than to suggest debating the current vice president?
Sen. Kelly Ayotte
Ayotte could help Romney in New Hampshire, an important swing state that neighbors Romney's political home of Massachusetts. But the Granite State went for Obama in 2008. Also, Ayotte would almost certainly help Romney close the gender gap against the president.
But there's also a question of experience and readiness.
"Even though she was state attorney general before she became senator, she's got the Palin problem of having been in major office only a year and a half," Sabato said. "I think she's well down on the list."
Rep. Paul Ryan
House Budget Chairman Ryan and former Romney primary rival Pawlenty have also showed they'd be good No. 2 picks.
Ryan has frequently pushed the Republicans' "class warfare" line against the president and has unveiled a budget that's a battle cry for many conservatives. Also, Ryan hails from Wisconsin, an important battleground, and his youthfulness could appeal to a group that the president enjoys advantages with.
Yet Democrats savor the opportunity to have Ryan's budget proposals -- which they liken to a war on the poor -- at the center of the presidential campaign.
Former Gov. Tim Pawlenty
As for Pawlenty, he's willingly spoken on behalf of the Romney campaign, relishing the attack dog role. In Romney's second general election ad, Pawlenty appears in the first four seconds, suggesting that his audition is going well.
Pawlenty has problems. The former Minnesota governor failed to make a dent in the GOP primaries and likely would have a problem helping Romney win Minnesota.
It's entirely possible that someone not currently auditioning to be Romney's running mate could win the VP process.
Former Gov. Sarah Palin
Then there's Sarah Palin.
In 2008, then-Alaska Gov. Palin was not high on the list of potentials and not widely seen as trying out for the job. And yet, after being picked, Palin did assume the traditional running mate's attack dog role.
And in yet another twist in the process, others had the VP job and did not assume the traditional attack role.
"Certain vice presidents just don't [fit that bill]," Brinkley said.
"You wouldn't expect George Herbert Walker Bush to do that for Ronald Reagan. It just wasn't in his personality. Or Al Gore to Bill Clinton. He just couldn't pull it off in a way."