I Was Wrong About Dick Cheney...

...and other lessons I learned from vetting vice-presidential candidates.

We've entered the silly season when vast numbers of words will be expended on who Mitt Romney's vice presidential running mate should be. Since the actual announcement is likely to be made shortly before the Aug. 31 GOP convention, we'll have to endure three-and-a-half months of pundits handicapping prospects.

This exercise is largely useless. Who thought at this point in 2000 that the vice-presidential nominees would be Dick Cheney and Joe Lieberman, or in 2008 Sarah Palin and Joe Biden?

The person who matters most in this decision, Mr. Romney, appears to be approaching it with appropriate seriousness, appointing a longtime trusted aide, Beth Myers, to vet possible running mates.

Having played a role in this process, I know that if done well this will be a political proctology exam for each individual considered. Ms. Myers and an army of lawyers, researchers and accountants will examine the person's every public statement, vote or executive decision; they will review tax returns and financial records; and they will scrutinize friends and associates. They also will ask finalists what in their background could embarrass Mr. Romney if it came out, because it will.

This is not an activity for the squeamish or reticent. Team Romney will discover that every prospect has strengths and warts. There is no perfect candidate.

Many presidential contenders view their potential vice president largely through an Electoral College prism: Who can deliver a vital state? This was John F. Kennedy's approach in 1960. He had little love for Lyndon Johnson but felt creating a Boston-Austin ticket could bring Texas into the Democratic fold. And the Lone Star State, which had twice chosen Eisenhower, went for Kennedy.

Sometimes the vice-presidential decision results from the campaign's flow. In 2008, John McCain's camp felt that while they were ahead after a better-than-expected summer, they needed to shake things up with an out-of-the-box pick. This thinking produced Sarah Palin.

That same year, Barack Obama left for a Hawaii vacation on Aug. 8 as Russia invaded Georgia. He worried about his absence of international experience and turned to Mr. Biden, chairman of the Senate Foreign Relations Committee.

But such political decisions run into one hard reality: Running mates haven't decided an election in more than a half-century. For example, research by Bernard Grofman and Reuben Kline, political scientists at the University of California, Irvine, suggests that the net impact of the vice-presidential picks in 2008 was roughly one-half of one point and is generally less than one percentage point. Presidential elections are rarely that close.

What about running mates helping to carry their home states? Political scientists Christopher Devine of Ohio State and Kyle Kopko of Elizabeth College argue the home-state advantage is often modest and almost never dispositive. Rarely does a presidential election come down to one state, as it did in 2000 (Florida) or 2004 (Ohio). In neither of those instances did either party field someone from those states.

A running mate's principal political impact is on behalf of the presidential candidate's themes or issues. The vice-presidential candidate helps reinforce what the presidential candidate is emphasizing. But if the top banana on the ballot isn't getting it done, the running mate won't be able to on his or her own.

Choosing a running mate reveals much about the presidential candidate himself. Though still only a candidate, this is his first presidential decision.

It is one best made by asking about the skills, philosophy, outlook, work ethic and chemistry of a prospective running mate. Do they have good judgment? Can they be counted on to give their unvarnished opinion? Are they loyal? Who can best help the president govern? In other words, set aside politics. Put governing first.

This was brought home to me in 2000, when then-Gov. George W. Bush was strongly leaning toward picking Dick Cheney as his VP. He knew I was opposed and invited me to make the case against his idea. I came to our meeting armed with eight political objections. Mr. Bush heard me out but with a twist: I explained my objections with Mr. Cheney sitting, mute and expressionless, next to the governor.

The next day, Mr. Bush called to say I was right. There would be real political problems if he chose Mr. Cheney. So solve them, he said. Politics was my responsibility. His job was different: to select his best partner in the White House and a person the country would have confidence in if something terrible happened to him. The country was better served by Mr. Bush's decision than by my advice.

There's a lesson there for Mr. Romney. Choose the best person for the job. Leave the politics to the staff.

This article originally appeared on WSJ.com on Wednesday, April 25, 2012.