'The most insignificant office'? John Adams didn't think much of the vice presidency. But this year, Barack Obama and John McCain have chosen running mates who could determine the outcome in November.

• Author: Bilyeu, Suzanne
• Position: Cover story

One percent: That's the portion of American voters who typically say vice-presidential candidates influence their decisions in a presidential election, according to Andrew Kohut of the Pew Research Center.

This year, however, may be a different story: The November election looks like it's going to be close, and the Biden/Palin vice-presidential matchup could be among the deciding factors.

There are two key reasons why the voters--and the media--are paying more attention to the candidates at the bottom of the ticket this year.

First, both running mates seem to have been chosen with an eye toward addressing perceived shortcomings at the top of their respective tickets.

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Senator Joe Biden of Delaware, 65, has spent 36 years in the Senate, which may alleviate voter concerns about Barack Obama's short time in Washington.

John McCain has plenty of experience, but hasn't generated the excitement on the campaign trail that Obama has. Governor Sarah Palin of Alaska, 44, the first woman on a Republican presidential ticket, seems to be providing plenty of excitement in her first weeks as his running mate, especially among conservative Republicans who have been lukewarm about McCain.

WHAT THE FOUNDERS THOUGHT

Second, the role of Vice President has changed in recent years: By all accounts, Presidents Bush and Clinton gave Vice Presidents Dick Cheney and A1 Gore more power and influence than any Vice Presidents in American history.

In fact, the importance of the No. 2 spot today would astound the Founding Fathers. Aside from taking over for a President who can no longer serve, the Constitution assigns the Vice President the responsibility for presiding over the Senate and breaking tie votes. Other than that, the job wasn't given much thought, according to Stanley N. Katz, a constitutional historian at Princeton University.

But the Vice President has always been--literally--a heartbeat away from the presidency, and many of these understudies have ended up stepping into the lead role.

Of the 46 Vice Presidents since 1789, 14--nearly a third--have become President. Nine got the job without being elected, when the President died in office or resigned. (See chart, p. 8.) Theodore Roosevelt, for example, became President after William McKinley was assassinated in 1901; John Tyler got the top job in 1841 when President William Henry Harrison caught pneumonia on a cold, snowy Inauguration Day and died after only a month in office; and in 1974, Gerald Ford moved up when Richard Nixon, facing impeachment over the Watergate scandal, became the first President to resign.

THE JOKES

Long before Jon Stewart and Jay Leno, the vice presidency was a target of jokes--often from Vice Presidents. John Adams, the first to hold the job, called it "the most insignificant office that ever the invention of man contrived or his imagination conceived." George Clinton, who became Thomas Jefferson's Vice President in 1805, called the job "a respectable retirement" after 18 years as New York's Governor.

In 1848, Senator Daniel Webster turned down an offer to be Zachary Taylor's running mate, saying, "I do not propose to be buried until I...