Jae C. Hong/AP
Republican presidential candidate Mitt Romney, joined by Sen. Marco Rubio, R-Fla., talks to reporters during a news conference in Aston, Pa., on Monday. Rubio is frequently mentioned as a potential running mate for Romney.
Ahead of Pennsylvania's primary Tuesday, the likely Republican presidential nominee has been campaigning in the state with a man at the center of running-mate speculation — Florida Sen. Marco Rubio. But Mitt Romney hasn't said much about whom he might name as his vice presidential choice.
Romney has said he appointed a longtime aide to handle the process and that he hasn't yet discussed making a list of potential candidates. But just about everyone else in politics is discussing it. And the men at the top of that list are asked about it a lot.
Here's a short list of some of the Republicans often mentioned as possible running mates for likely GOP nominee Mitt Romney:
Current job: U.S. senator from Florida
Past posts: Speaker of the Florida House of Representatives; member of the West Miami City Commission
Known for: His appeal to Tea Party supporters and his Cuban heritage
Current job: U.S. senator from Ohio
Past posts: Director of the Office of Management and Budget and U.S. trade representative under President George W. Bush; U.S. representative from Ohio; director of the Office of Legislative Affairs and associate counsel to President George H.W. Bush
Known for: His budget expertise and his ability to win in the key swing state of Ohio
Current job: U.S. representative from Wisconsin and chairman of the House Budget Committee
Past posts: Legislative director for Sen. Sam Brownback, R-Kan.; staff assistant at Empower America; aide to Sen. Robert Kasten, R-Wis.
Known for: His budget-drafting prowess and conservative bona fides
Current job: Governor of Virginia
Past posts: Attorney general of Virginia; member of the Virginia House of Delegates; prosecutor in Virginia Beach, Va.; 21 years in the U.S. Army
Known for: Winning in the swing state of Virginia by a wide margin in 2009
Current job: Governor of Indiana
Past posts: Director of the Office of Management and Budget under President George W. Bush; president of Eli Lilly and Co.'s North American pharmaceutical operations; CEO of the Hudson Institute; adviser to President Ronald Reagan; chief of staff to Sen. Richard Lugar, R-Ind.
Known for: Flirting with a run for the GOP nomination before saying he had to put his family first
Sources: Biographical Directory of the U.S. Congress; Virginia.gov; IN.gov
New Jersey Gov. Chris Christie — a Tea Party favorite and early Romney supporter — seems to have ruled it out, telling one inquirer that people might not find his personality "best suited to being No. 2." When other short-listers are asked whether they'd accept the position — Wisconsin Rep. Paul Ryan, Virginia Gov. Bob McDonnell, Ohio Sen. Rob Portman and Florida's Rubio — all seem to leave the door open, without answering directly.
'Don't Blow It'
There's no formula for picking a running mate. Some of those names might help Romney win an important state or reach out to a key voting group, like Hispanics. But there is one bottom line, says Gary Bauer, a social conservative leader and one-time Republican presidential candidate: "My advice is don't blow it."
Romney is working hard to win over the conservative activists who weren't with him in the primaries. He gave a big speech at the NRA this month and is scheduled to speak at Jerry Falwell's Liberty University next month.
But there's surprisingly little pressure now on Romney to pick a recognized social conservative as vice president, like a Rick Santorum or a Mike Huckabee. Bauer says that's because there is no one on Romney's short list whom conservatives would reject.
"I don't see anybody being mentioned who is wrong on the values issues, who is wrong on the need for a strong national defense [or] who is questionable on the size of government," Bauer says. "When [John] McCain ran, there were some people being mentioned that were pro-choice on the abortion issue ... and there was a collective sigh of relief when he went with Sarah Palin. I don't see that now."
Lessons From McCain-Palin
Four years ago, McCain wanted to run with his friend Sen. Joe Lieberman, who, as Bauer points out, supported abortion rights. The base wouldn't have it. McCain was also running behind Barack Obama at the time, and the idea was to create a dynamic moment in the campaign with the choice of then-Alaska Gov. Palin.
"We were behind, we made decisions under political pressure, and I think that there [are] a lot of lessons to be learned from that," says Steven Schmidt, McCain's top strategist at the time.
Schmidt says the circumstances for Romney are much better, and he's more competitive financially and politically than McCain was at this time four years ago.
"We were so desperate to come up with a way to win, and, you know, that led to the picking of Gov. Palin," he says. "When you look at the Romney campaign right now, I think that the lessons from 2008 won't be lost on them. They'll run a very, very tight process, and the result will be ... someone who is ready and universally recognized as ready to be commander in chief from day one."
That's the most important thing about choosing a running mate, whether Romney wants that person to help him to win a state or an ethnic group, or to reinforce his own brand.
Veterans of vice-president vetting say it is a mistake to overdo the political calculations, and the most important qualification for a vice presidential candidate is a closet free of skeletons and the ability to do the job — of president — at a moment's notice.