Mitt Romney may be preparing to unveil his running mate sooner rather than later, amid speculation the Republican White House contender is seeking to shift the spotlight away from his business and tax records.

Some observers have honed in on this week, and notably Romney's appearance at a campaign event in the must-win state of Ohio on Wednesday, as one in the narrowing list of possible periods in which the candidate may announce who will be on his ticket as he challenges President Barack Obama in November.

The question is: will Romney make a safe pick -- Senator Rob Portman of Ohio and former Minnesota governor Tim Pawlenty top most short lists -- or will he go for a riskier but energizing choice, like ex-secretary of state Condoleezza Rice or Senator Marco Rubio of Florida, that could set a spark to his campaign?

Candidates divulge little about the secretive VP vetting process, and Romney has clamped a corporate-style seal around the all-important operation.

But hints have trickled out, including a New York Times report Monday which cited Romney friends saying they believe he has made his decision and it could be announced as soon as this week.

The campaign offered a tease of its own on Tuesday, announcing directors of operations and communications for the vice presidential candidate.

Picks are usually announced much closer to or during the party's national convention, which for Republicans this year is late August.

"However, the general election campaign has begun early with an unusually large amount of money already being spent," Allan Lichtman, an American University professor and expert on presidential campaigns, told AFP.

"Romney also wants to divert the conversation from his role at Bain and his tax returns."

The candidate, a multimillionaire and former governor of Massachusetts, has been pummeled in recent weeks over his time at Bain Capital, the private equity firm he founded and led for 15 years.

The Obama camp argues Romney presided over the firm when it bought up US companies that then shipped jobs to low-wage economies overseas.

Romney also faces pressure to release more than his promised two years of tax returns, as recent reports have drilled into his lucrative holdings in offshore tax havens.

He travels abroad in late July, and some say Romney would be jumping the gun if he makes the VP announcement before his trip.

"The longer he can tease the decision, the better," said Matt Dickinson, a political science professor at Middlebury College.

"The ideal rollout is to make the announcement during the convention... for maximum suspense and exposure."

The Times piece focused on Pawlenty, a truckdriver's son with down-to-earth appeal who could help counter the image of Romney as an elite businessman.

"T-Paw" is also an evangelical Christian, which could assuage religious conservatives wary of Romney's Mormon faith.

But Dickinson said Pawlenty lacks the "pizzazz factor," and brings little to the table other than his workingman roots and extensive experience on the stump for Romney.

He thinks Portman is the top choice, a levelheaded senator who served in two cabinet posts as George W. Bush's trade representative and budget director, and who can deliver perhaps the most crucial state of the entire election.

"He can balance Mitt's private sector background with his own inside-the-beltway (Washington) experience and knowledge of the federal budget," Dickinson said.

Portman has played down the VP conjecture, and on Tuesday told Fox News that "I have not" heard recently from Romney about the job.

Also in the "veepstakes" is New Mexico's Susana Martinez, who could kill two birds with one stone as the nation's first Hispanic female governor.

But Martinez may have too many similarities with Sarah Palin as a popular new governor from a small state who has little national exposure.

Undoubtedly in the back of Romney's mind is his predecessor John McCain's rebellious pick of political unknown Palin, the governor of Alaska who at first fired up the conservative base but wound up as a liability.

The charismatic Rubio is routinely mentioned as a possible running mate. Romney may hope the son of Cuban immigrants can help in key state Florida and other battlegrounds that have large Hispanic populations.

But he has less experience than Obama did when he ran in 2008, and some observers worry there may be skeletons lurking in the cupboard.

Ultimately, Dickinson believes, Romney is not going to gamble.

"I think he would feel more comfortable with a safe pick," the professor said. "The idea here is not to take the focus away from the central issue of this campaign, which is Obama and the economy."

[Photo credit: Maria Dryfhout /]