Several months ago, we met a CEO who had one main complaint about his job. It wasn’t foreign competition or fickle consumers. No, it was loneliness. “I make every decision by myself,” he moaned.

“That’s nuts!” was our immediate reply. “You can’t run the place that way!”

Every leader needs a team, and every leader benefits enormously from having a wingman, a partner who can be counted on to counsel, goad, provoke, listen, and on and on. It’s true in business, and it’s true in politics. A great person in the No. 2 spot can make the person at No. 1 decidedly stronger, smarter and more effective.

So, Mitt Romney, don’t blow the VP thing.

Fortunately, that would be pretty hard at this point. The current short list of contenders easily passes muster in terms of intellectual heft and leadership experience: Florida Senator Marco Rubio, Senator Rob Portman of Ohio, Representative Paul Ryan of Wisconsin, Governor Chris Christie of New Jersey and Governor Bob McDonnell of Virginia. There’s not an iffy option in the bunch.

So how should Romney choose among them? To answer that question, we’ve put together a scorecard that rates each candidate against six criteria we consider essential in a vice-president.