— 4. A bold running mate choice can energize an otherwise moribund campaign.
This seemed to happen when McCain chose Palin, which electrified the Republican base, but McCain still lost decisively, and Palin's miscues and combative nature as a self-described "mama grizzly" may have negated any sizzle she gave the ticket.
Presidential candidates do not want to be upstaged by their running mates. They think the election is about them — and it is, as surveys consistently show. History reinforces the polling; selections such as Spiro Agnew and Dan Quayle received heavy media criticism, but each was on the winning side.
But sometimes when the odds are long, a presidential nominee believes he can boost his chances with an exciting vice presidential choice. That was part of Mondale's thinking in 1984 when he selected Geraldine Ferraro, a congresswoman from New York, to be the first female vice presidential nominee for a major party. But this was after the National Organization for Women demanded that Mondale select a woman, muting the impact of his choice. Rather than a pioneering leader, Mondale seemed simply to be captive to another special interest. He lost 49 states to Ronald Reagan.
Polls show that the 2012 race should be close, but Romney is running far behind among Hispanic voters, the nation's fastest-growing demographic. He could turn to Sen. Marco Rubio of Florida or Nevada Gov. Brian Sandoval to try to change that, but obvious pandering is poor politics — and inexperience on the national stage could cause problems.
5. A nominee's selection of a running mate reveals how he would govern.
Choosing a running mate is more about politics than governance.
As recently as 1920, when convention delegates ignored Warren Harding's choice of a running mate and selected Calvin Coolidge instead, presidential nominees had very little to say about who their running mate would be. But in recent decades, presidential nominees have become increasingly engaged in the vetting and selection process because none of them want a repeat of the debacle of 1972, when George McGovern had to drop Thomas Eagleton from the ticket after revelations that Eagleton had undergone electroshock therapy.