If Mitt Romney goes on to win big in Tuesday’s Republican presidential primary and pile up victories in February and on Super Tuesday (March 6), the vice-presidential buzz will start in earnest. Rather than begin with names, it is more useful first to think about the considerations that go into the VP selection. Any presidential nominee is going to want someone who could assume the presidency if need be and who is trustworthy and discreet. But there are two schools of thought in vice-presidential selection.

The first is “amplification.” Bill Clinton selected Al Gore to highlight the New South, moderate-reformer message he was trying to convey. To a certain extent, Gore did the same in selecting a moderate, pro-defense Democrat, Connecticut Sen. Joe Lieberman in 2000.

The alternative is the “balancing”approach. Barack Obama selected Joe Biden as a Washington insider, foreign policy “guru” (don’t laugh, this was his rationale) and blue-collar-friendly running mate. Likewise, George W. Bush selected the Washington-experienced, former defense secretary, Dick Cheney.

Turning to Mitt Romney, an “amplification” choice would be someone else with executive power, a sober and reasoned approach to governance and experience beyond the Beltway. Romney, if he went this route, would be looking to make the competence argument, highlight President Obama’s mismanagement of the economy and rely on voters’ general distaste for those who’ve made their career in Washington. He’d be willing to give up charisma and bank on his own appeal to independent voters anxious to get rid of Obama.

However, if Romney is looking for a VP to balance the ticket, he might look for a feistier personality, someone popular with the GOP base who nevertheless has D.C. experience, and a candidate with appeal to working- and middle-class voters. This would perhaps involve some risk-taking. He might get a candidate whose personality could sometimes steal the limelight. He could get a candidate with a record of criticizing him or his policies, which would surely be exploited by the media and the Obama team. However, balance in the context of a presidential ticket tends not to refer these days to geographic balance. (Perhaps presidential candidates have figured out that VP nominees don’t “deliver” states anymore.)

So which potential VPs would fit into the two categories? An amplification choice would likely be a Republican governor or someone with extensive executive experience: Virginia Gov. Bob McDonnell, Louisiana Gov. Bobby Jindal, Indiana Gov. Mitch Daniels, Sen. Rob Portman of Ohio (whose career includes head of the Office of Management and Budget and U.S. trade representative), Ohio Gov. John Kasich (yes, he has D.C. legislative experience, too), and former Minnesota governor Tim Pawlenty. The risk here is a ticket too bland and too cautious to connect with voters and fire up the base. (More exciting choices might be former New Hampshire attorney general and now Sen. Kelly Ayotte or New Mexico Gov. Susana Martinez). None of these choices would damage Romney, but it’s not clear that any would be a real asset in winning the election.

In the “balancing” category would be Sen. Marco Rubio (R-Fla.), Sen. Jon Kyl (R-Ariz.) and current rival Rick Santorum. These are all rock-solid conservatives with some verve and appeal beyond the traditional GOP base. All have D.C. experience but with a track record of advancing the conservative agenda.

Now both Rep. Paul Ryan (R-Wis.) and New Jersey Gov. Chris Christie have both amplification and balancing qualities but would be most notable, I would argue, for their contrasts with Romney. Granted Christie is also an executive, but it is his bluntness, combativeness and charisma that would provide a contrast with Romney. Ryan, likewise, would provide some amplification for Romney. (They share wonkishness on policy, a penchant for detail and an aura of competence.) But, like Christie’s, Ryan’s contrasts with Romney — his ability to energize the base, his ability to articulate conservative ideology, legislative and D.C. experience and his appeal to ordinary suburban voters — are what are most noteworthy.

My own preference would be to go bolder, broaden his appeal and find someone who can pep up the base without alienating independent voters. Should Romney go in this direction it would show a certain confidence (i.e., he’s not afraid of being overshadowed). And really, can you imagine Christie, Rubio or Ryan debating Biden? Oh my! That could be the highlight of the whole campaign.