A map for choosing between the candidates.

Imagine for a moment you're a member of what's becoming the most scrutinized group of political players in years: the 796 superdelegates to the Democratic National Convention. You are unbound by any rule or custom in choosing whether to vote for either Hillary Clinton or Barack Obama. It's increasingly likely that you and your fellow supers—senators, House members, governors, state party chairs, national committee members, and other worthies—will hold the key to the nomination. So, how do you decide whom to support?

Let's assume you're determined to apply the soundest principles of fairness and justice (I know, I know, you're a political animal, but indulge me). Let's also assume that you've somehow put on one of John Rawls' "veils of ignorance," which means you're making your decision free of knowing which candidate would benefit from it. What, then, are the questions you need to answer?

Are you more like a presidential elector or an elected legislator? Whatever the original intention of the founders, presidential electors—the 538 folks who actually cast the votes that elect the president—are supposed to be automatons. (Here's my satiric look at what happens when they refuse to act the part.) As far back as the first contested election, an angry Pennsylvania voter wrote to the Gazette of the United States, "What, do I choose Samuel Miles to determine for me whether John Adams or Thomas Jefferson shall be President? No! I choose him to act, not to think."

When the 2000 election ended in a dead heat, a Bush elector wrapped in a veil of ignorance might have decided to abstain or to vote for a third candidate, on the ground that no clear winner could conceivably be determined in so close a contest. If two of the 271 electors had done that, Bush would have been deprived of an electoral majority, and the election would have been thrown into the House of Representatives. But not one did; they were following the choice of the voters who had chosen them. By this standard, the job of the superdelegates is to follow the will of the voters, not to substitute their judgment. But don't be fooled into thinking the problem is solved if you decide to do this. There's a trickier question lurking:

Which voters will you follow? Suppose you're a member of the House of Representatives and your district voted for Obama, your state voted for Clinton, and Obama has won the votes of more primary and caucus participants nationally. Whose will are you supposed to reflect? Does it make a difference if you're a governor or senator (follow the state?) or a national committee member (reflect the national total)? Suppose at the end of the process, one candidate has more delegates and the other has won more votes? (Let's not even think about whether you plan to count the votes of Florida and Michigan Democrats when you figure out the total vote.)

How decisive must the vote be? In 1984, the spread in pledged delegates between Walter Mondale and Gary Hart was narrow, but Mondale had more of them than Hart did and had won a small plurality of the total votes cast. The superdelegates, in their first appearance at a Democratic convention, provided a substantial part of his 1,000-vote margin when the first and only ballot was taken. In the five elections since, the winning Democratic candidate wrapped up the nomination long before the convention.