When presidential nominees are asked about selecting a running mate, the answer almost always is: The choice should be the person most qualified to become president if fate or circumstance were to so dictate.
The first two vice presidents, John Adams and Thomas Jefferson, fit that description. But each got the job by the vote of the electoral college, with the higher vote-getter becoming president and the runner-up his standby.
In 1800, however, a tie there between Jefferson and Aaron Burr led under the Constitution to a vote in the House of Representatives. After 36 ballots, the Virginian carried the day and Burr had to settle for the vice presidency.