How It Works
Why do primaries continue after the battle is over?
Selection of delegates, other contests play role
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WASHINGTON (CNN) -- Does this make sense? Illinois is holding presidential primaries Tuesday -- even though the nominations of both parties have already been locked up.
But there's more to the primaries than selecting a presidential nominee as this week's "How it Works" explains.
The primaries and caucuses are the means by which delegates to the nominating conventions are selected.
And delegates aren't just voting on a party nominee at the convention. They're voting on the party platform, which tackles a host of issues ranging from abortion to defense.
"These delegates help to ensure that states will be represented," said Anthony Corrado, an expert on presidential elections at the Brookings Institution, a Washington think tank.
There are other reasons the primaries continue. The contests help to motivate the party faithful, a critical issue for both Democrats and Republicans, who want their supporters to turn out in big numbers in November.
So the candidates stay on the campaign trail. Nothing motivates the true believer -- or helps raise cash -- like seeing a candidate in the flesh.
And the question of a presidential nominee isn't the only the only thing on the ballot for most of the states holding contests.
Of the 16 states still to hold presidential primaries or caucuses, 12 are holding primaries for U.S. House seats and eight have Senate primaries the same day.
For example, Tuesday's primaries in Illinois feature wide-open and hotly contested U.S. Senate races for both parties.
On April 27 in Pennsylvania, Republican Sen. Arlen Specter faces a spirited primary challenge from U.S. Rep. Pat Toomey, who says Specter is too liberal.
While the primaries and caucuses continue, Corrado said the turnout is generally smaller for those states that hold them after the battle is effectively over -- as is the case now.
The state contests continue until June 8.