Choosing a No. 2: The ins and outs

The sight of Barack Obama and Hillary Rodham Clinton together in Unity, N.H., is sure to refuel the endless guessing game over who will occupy the second spots on the major-party tickets. There's no way to anticipate the thought processes of Democrat Obama and Republican John McCain, no formula for weighing the factors involved.

And this year, as ever, lessons learned seem to have been forgotten. Consider that much of the speculation has centered on individuals presumed to be able to deliver their states in November - even though few running mates have delivered states before, and current polls suggest it's not likely to happen in 2008, either. Obama and McCain could announce their picks at any time between now and the late-summer conventions. History suggests later rather than sooner; nominees tend to want to weigh their options as long as possible. In the end, of course, few Americans will ...