Decision time for the Democrats

Who are these superdelegates?
Basically they're the party bigwigs, men like Jimmy Carter, George McGovern and Edward Kennedy. The list of Democrat superdelegates comprises all former Democratic presidents, vice-presidents and party leaders (a group, 19 in all, known as the Distinguished Party Leaders); all serving Democrat members of the US Senate (48) and US House of Representatives (222); all Democratic state Governors (31); 398 members of the party's national body, the Democratic National Committee; and a number of "add-on delegates" selected by state party leaders. But the crucial thing about these superdelegates, 796 in total, is that – unlike ordinary delegates – not one has been chosen by popular vote in the presidential nomination process.

And why have they suddenly assumed such importance?
Owing to the unusually tight race between Barack Obama and Hillary Clinton. The Republicans, too, will have superdelegates at their national convention at the end of summer; but because John McCain has won so many elected delegates – "pledged" to support him as a result of his victories in state primaries or caucuses – he won't have to rely on unelected superdelegates to carry the convention. By contrast, the Democrat candidates are neck and neck. Barack Obama now has 1,598 pledged delegates to Clinton's 1,446; but both need 2,025 to win, and though five states have yet to vote, their pledged delegates will be carved up too evenly for either to triumph. So everything will depend on how those 796 superdelegates – 20% of the total number of Democratic delegates to the convention – decide to vote.

How have the Democrats got in this pickle?
Partly by having two strong candidates appealing to different sections of the core democrat vote: Obama scoring highly among African Americans and white university-educated liberals; Clinton among the white working class. And partly owing to Democrat devotion to electoral fairness. In most Republican primaries or caucuses, the candidate who wins the most votes in a given state picks up all the delegates which that state sends to the national convention. But Democrat rules mandate that every candidate with more than 15% of the vote in the state in question should be allocated delegates in proportion to his or her share of the votes cast in the primary. So even when Obama came second, he still picked up delegates. Had the Democrats used the Republican system, Hillary