Governors might make for better presidential candidates than senators do, but they have not had an advantage when it comes time for a party to pick its vice-presidential nominee.
Since the end of World War II, in fact, only 4 of the 25 men and women nominated for vice president by a major-party ticket had previously served as governors: Earl Warren in 1948, Edmund S. Muskie in 1968, Spiro T. Agnew in 1968 and 1972, and Sarah Palin in 2008. And Mr. Muskie’s experience had come earlier: he was one of Maine’s senators at the time that Hubert H. Humphrey picked him.
If Mitt Romney wins the Republican nomination, he will have an opportunity to break this precedent. Nobody knows what Mr. Romney’s short list would look like, but the one the news media is speculating about includes a number of current or former governors, like Chris Christie of New Jersey, Bob McDonnell of Virginia and Susana Martinez of New Mexico.
If Mr. Romney picked one of those governors — or another like Bobby Jindal of Louisiana or Mitch Daniels of Indiana — he could offer voters their first double-governor ticket since Republicans nominated Thomas E. Dewey of New York and Earl Warren of California in 1948.
It might just be a coincidence that so few governors have been picked, but I am guessing that it is not.
The first rule of picking a vice president is that he or she should do no harm — a criterion that may have increased in importance since John McCain picked Ms. Palin in 2008.
There are four ways that a vice-presidential nominee could potentially hurt the ticket: by being unready, undisciplined, unvetted or unpopular. Governors are probably worse than senators by a couple of these measures.
There is, obviously, little reason for a president to pick a running mate who starts out as being unpopular with the general public. Often, in fact, they have resorted to relatively unknown names — like Ms. Palin, Gerladine A. Ferraro, Dick Cheney or Dan Quayle — rather than select someone who had built up a national reputation with voters.
By this score, governors might be better than members of Congress. Incumbents are unpopular in general these days, but especially if they serve in Congress — which is why Mr. McCain may have picked someone who lived 3,300 miles away from Washington.
But being an outsider increases the risk that the candidate will be unvetted — and turn into a nasty October surprise for the campaign. The best defense against this is to pick someone who has run a campaign for president or vice president before and faced the full rigors of the news media spotlight. Few of Mr. Romney’s more likely nominees fit this description: of the 12 potential candidates that the betting market Intrade gives Republicans at least a 2 percent chance of picking as their vice president, only Rick Santorum has run a national campaign before.
Running for office in an especially high-profile state like California or New York might be a substitute, but with those exceptions, the best preparation might be serving in Congress under the watchful eyes of the national media.
Not all members of Congress maintain a high profile or compel constant attention, but there is at least some baseline level of scrutiny if they live and work in Washington. By contrast, states can vary in how rough-and-tumble their political cultures are and in how much scrutiny their elected officials receive, especially with state and local news bureaus being cut.
Although the historical record is spotty on this, there is also some evidence that governors are at greater risk of getting themselves into very severe scandals than senators are. Historically, seven senators have either been expelled because of a scandal or have resigned under expulsion proceedings, not counting senators expelled for supporting the Confederate rebellion. By contrast, even though there are only half as many governors as senators, 11 have either been impeached, removed from office by court or resigned under impeachment proceedings, while another 11 governors have resigned under scandal before facing potential impeachment. And the only vice president to resign under scandal, Mr. Agnew, was a former governor.
The risk that a vice-presidential candidate might be viewed as unready by the voters is another thing that campaigns want to avoid — if the president dies and the phone rings at 3 a.m. in a national emergency, are they ready to take the call?
Here, although governors’ executive experience might otherwise be an asset, they will not usually have acquired foreign policy or national security experience, whereas senators can serve on foreign policy committees and must make votes and take positions on world affairs.
Vice-presidential nominees have quite often had foreign policy experience, even when — like Dick Cheney in 2000, George H.W. Bush in 1980 or Sargent Shriver in 1972 — they had never been elected to an office higher than the United States House or never been elected to any office at all.
The final risk is that a vice-presidential candidate might be undisciplined and commit a substantial gaffe, step on the message of his campaign, or simply upstage the presidential candidate even if their intentions are good. This can also be a problem for governors, who are used to being in charge and not playing second fiddle. One also imagines that Mr. Romney — who has been a chief executive for most of his life and who has sometimes reacted badly when having his authority challenged during the campaign — might be especially keen to avoid a clash or ideas or personalities.
This is not to say that candidates like Mr. Christie or Mr. McDonnell would be inherently poor choices, but Republicans have a lot of fairly good ones — in some ways, in fact, their list of potential vice-presidential candidates is more impressive than their presidential candidates.
Unless Mr. Romney is trailing badly in the polls by the summer, he might elect to play it safe, and congressmen are probably safer and more manageable vice-presidential choices than governors are.