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In a normal year, hardly anyone pays attention to the detailed rules of individual states’ primaries. But this is not a normal year. Candidates in both parties are so closely bunched up that campaign workers are feverishly studying the arcane rules of each state’s primary in hopes of gaining even a slight advantage. Two issues in particular are important in each state:

OPEN VS. CLOSED PRIMARY

Some states hold closed primaries, meaning only a party’s members can vote. Others have open primaries, so people from outside the party can participate. What it means: Open primaries are generally better for candidates with crossover appeal, like Sens. Barack Obama and John McCain, because independents can jump in and support them. In some states, Obama and McCain have found themselves battling each other for independent voters.

PROPORTIONALITY

A state’s delegates can be awarded either proportionally or on a winner-take-all basis. All the Democratic primaries are proportional. The Republican primaries, in contrast, vary by state.

What it means: If a state is winner-take-all, a favored candidate in theory may not have to campaign much there, knowing he or she will likely get all that state’s delegates. If a state is propotional, however, the margin of victory becomes important, and a second- place finish can still garner a lot of delegates. Even if Sen. Hillary Clinton wins New York, for example, Obama could get many of its 202 delegates, and it might be worthwhile for him to campaign in targeted areas of the state.

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IN THE WEB EDITION: For the Tribune’s detailed look at the candidates and the campaign and more from The Swamp, go to chicagotribune.com/elections