WITH the nomination fights over but the conventions not yet called to order, political attention naturally falls on a post that, in most administrations, gets no attention whatsoever. That is the vice presidency, "the most insignificant office," John Adams, its first occupant, said, "that ever the invention of man contrived."
So insignificant that Daniel Webster refused the nomination in 1828, saying that he did not "propose to be buried until I am dead." Precisely a century and a half later, Walter Mondale, then vice president in the Jimmy Carter administration, said that, if you "want to talk to someone who is not busy, call the vice president."
But the vice presidency is important in three circumstances - when a president dies or resigns, when a president, like Jimmy Carter, Bill Clinton, and George W. Bush, gives extraordinary power to his understudy, and when a presidential nominee struggles with the challenge of winning the fall election.
So while Dick Cheney, almost certainly the most influential vice president in American history, still occupies the house on Observatory Hill in northwest Washington and while Sen. John McCain and Sen. Barack Obama wrestle with their own choices for running mates, the vice presidency seems far less of an irrelevancy.
There's no formula for this choice, except maybe the notion, often attributed to Richard Nixon, that a presidential candidate should consider his running mate a success if he carries his own state. Every winning ticket since 1972 has redeemed the Nixon formula. (The irony is that the last winning ticket where the vice-presidential nominee failed to carry his own state was the Nixon ticket in 1968, when Gov. Spiro Agnew lost Maryland by more than 20,000 votes.)
This doesn't always work. Many losing tickets lose the home state of the vice-presidential nominee. The Democrats lost North Carolina in 2004 (John Edwards), New York in 1984 (Geraldine Ferraro), and Maryland in 1972 (R. Sargent Shriver). The Republicans lost New York in 1964 (William E. Miller) and in 1996 (Jack F. Kemp).
Twice since 1960, parties have tried to rig the system by nominating running mates from the same state as their rivals' presidential nominee. Both times (in 1960, when GOP presidential candidate Nixon chose Henry Cabot Lodge of Massachusetts in his effort to beat John F. Kennedy, and in 1988, when Democrat Michael Dukakis chose Lloyd Bentsen of Texas in his effort to defeat George H.W. Bush) the gambit failed.
There are lots of balancing acts in this process: Pair a candidate experienced in domestic affairs (Ronald Reagan, 1980) with one steeped in foreign policy (George H.W. Bush). Put a candidate light on experience (John F. Kennedy, 1960) with one heavy on experience (Lyndon B. Johnson). Place a candidate from a state in the Old Confederacy (Johnson, 1964, from Texas) with one in the liberal north (Hubert H. Humphrey of Minnesota).
But balance isn't always the way to go, or else a young, Southern presidential candidate (Bill Clinton, 1992) would not have chosen a young, Southern running mate (Al Gore) from a state, Tennessee, that shared a border with his own state, Arkansas. That ticket defeated the exquisitely balanced Republican ticket of an experienced executive from a Southern state (George H.W. Bush) with a young, onetime senator from the North (Dan Quayle).
The choice of a running mate is often described as a good indicator of how a potential president makes decisions - what factors the nominee weighs, how decisive he is, how willing he is to do what is best for the party (or the country) rather than what is best for his own comfort and sensibility.
Often it comes down to an internal struggle between what a candidate wants versus what a candidate needs.
This spring, the Miller Center of Public Affairs at the University of Virginia published excerpts from an interview with Republican strategist Stuart Spencer that was conducted for the center's Reagan Oral History Project.
Mr. Spencer related that when he and Reagan flew to the Republican National Convention in 1980, Reagan "spent 20 minutes dumping on George Bush" during the flight. Then Mr. Spencer told the presumptive GOP nominee that he was going to end up selecting Mr. Bush as his running mate.
"He said, 'Why?,' I said, 'Because you need him.'•"
Mr. Spencer was involved with Mr. Bush's 1988 presidential campaign, as well, and the situation couldn't have been more different. While Reagan had made the selection he needed, Mr. Bush made the selection he wanted.
"[Mr. Bush] decided all presidents have a stubborn quality. He's stubborn. Reagan could be stubborn. Ford could really be stubborn. He decides he's going to pick his vice president. Somewhere along the line he [Bush] was going to go with Quayle. He didn't tell anybody that."
So the first thing a nominee has to do is to leak a list of names. Both the Obama and McCain camps are doing that already. They don't want a repeat of the Quayle experience, where at the New Orleans convention in 1988 a mob of reporters greeted a newly minted vice-presidential choice who hadn't been vetted - a spectacle Mr. Spencer described as "5,000 animals who don't know who he is and are mad because they hadn't guessed."
Leaking the names allows the press to help test the candidates and marks the point when the real decision-making begins.
Choosing a vice presidential candidate is the first important choice a presidential nominee makes. In most cases how the decision is made is far more important than what the decision is. But not always. In the case of George W. Bush in 2000, the identity of the choice was by far the most important part of it.