As part of the proportional system [that the Democratic party uses to award delegates from a given state based on percentage of votes won], Democrats award delegates based on statewide vote totals as well as results in individual congressional districts. The delegates, however, are not distributed evenly within a state, like they are in the Republican system.
Under Democratic rules, congressional districts with a history of strong support for Democratic candidates are rewarded with more delegates than districts that are more Republican. Some districts packed with Democratic voters can have as many as eight or nine delegates up for grabs, while more Republican districts in the same state have three or four.
The system is designed to benefit candidates who do well among loyal Democratic constituencies, and none is more loyal than black voters. Obama, who would be the first black candidate nominated by a major political party, has been winning 80 percent to 90 percent of the black vote in most primaries, according to exit polls.
"Black districts always have a large number of delegates because they are the highest performers for the Democratic Party," said Elaine Kamarck, a Harvard University professor who is writing a book about the Democratic nominating process.Plus, Obama's campaign had the foresight to plan for a long primary season because the Democratic Party's nomination procedures are designed for that:
The system enables strong second-place candidates to stay competitive and extend the race - as long as they don't run out of campaign money.
"For people who want a campaign to end quickly, proportional allocation is a bad system," [Democratic strategist Tad] Devine said. "For people who want a system that is fair and reflective of the voters, it's a much better system."