While the main event goes on in the Republican presidential primary race, the VP shortlist contenders are biding their time. Several in the top tier of possible candidates did themselves some good recently.

Despite the flap over the abortion ultrasound bill, Virginia Gov. Bob McDonnell still has sky-high approval ratings. In the Roanoke college poll, his approval, measured during a time the controversy was ongoing, clocked in at 60 percent. That makes him one of the most popular governors and adds to his credibility as a running mate for the GOP presidential nominee. His run in 2009 and his governorship are an example to the presidential contenders. His social-conservative credentials are rock-solid, but he has governed as a conservative pragmatist and worked well with Democrats. He’s also done his bit in blasting Senate Democrats for their inactivity.

Meanwhile, the other much-talked about VP contender, New Jersey Gov. Chris Christie, who has been confrontational and controversial in a deep-blue state, has an approval rating of 55 percent. He also is a model for Republicans: Fight on conservative principles, engage the media and find a really good foil (the teachers’ union). More important, on Sunday he said in public what he has said privately about his willingness to be VP: “If Gov. [Mitt] Romney were to come and talk to me about it, I’d listen, because I love my party enough and I love my country enough to listen.”

Then there is Sen. Marco Rubio (Florida). Unlike Christie and McDonnell, he has not endorsed Romney nor spent considerable time with him. (Do not underestimate the importance of a personal comfort level in the VP decision-making process.) Rubio did, however, do his part in batting down Newt Gingrich during a critical period in the Florida primary race. His approval rating has been in the 40s lately with Florida voters, but he remains a rock star in the Republican Party at large. On Feb. 20, this quote appeared at the top of a poll by Fairleigh Dickinson University’s PublicMind: “Asked who should be the Republican nominee for Vice President, Florida’s Senator Marco Rubio tops the list, followed by the surging former Pennsylvania Senator, Rick Santorum, and New Jersey’s unvarnished Governor Chris Christie, according to a new national poll of registered voters by Fairleigh Dickinson University’s PublicMind.”

Whether Rubio’s experience and relationship with Romney are sufficient to get him the nod is uncertain. And, unlike the two governors, he’s been rather blunt in saying that he doesn’t want the job.

Then there are the solid and well-spoken Republican lawmakers, including Sens. Jon Kyl (Arizona) and Pat Toomey (Pennsylvania) and Rep. Paul Ryan (Wisconsin). They are handicapped by events beyond their control: The antipathy toward Congress and Romney’s anti-D.C.-insider message. As Congress does less and less this year (after the payroll tax cut extension, it might have virtually no accomplishments) these members will need to raise their own profiles if they want to remain in the VP mix.

Nevertheless, Rubio, Toomey and Kyl all got a boost from the conservative Club for Growth today, which announced: “Senators Pat Toomey (PA), Marco Rubio (FL), Dan Coats (IN), Kelly Ayotte (NH), Jon Kyl (AZ), and Jim Inhofe (OK) had 2011 scores and LifeScores high enough to qualify for the Defender of Economic Freedom Award.”

For now, Christie and McDonnell remain the front-runners for the VP pick, with Rubio as the sentimental favorite.