Of course it doesn't matter at general election time, it is a given that obama will win in Illinois but this is a primary election and those votes are extremely important to Gingrich, Santorum, Paul and Romney.
I wouldn't miss it for anything, it's the only time in this election when my vote will mean anything. I will not be voting for Romney or Paul or Romney.
(Yes, I know I said Romney twice, that was for emphasis!)
We will see this more and more in all the “open” primaries to come. Look for Santorum’s actual numbers to be about 6 to 8% higher than predicted.
I live near Chicago, and I know that Illinois will be a swing state, in the general election, based on the 2010 election results. In that year, Illinois elected a Republican to the U.S. Senate, to replace a retiring Democrat. In 2010, IL Republicans gained four seats, in the U.S. House. Republicans gained seats, in the state senate and state house.
Illinois is the first of three DIRECT DELEGATE ELECTION primaries (which are like winner-take-all by district). Which candidate you vote for doesn't count for anything. You have to vote for the delegates directly on the ballot. The delegates are marked for which candidate they're supporting. Whichever 3 or 4 delegates in the district get the most votes are the winners. So if Romney's 3 or 4 delegates get 35% each, and no other delegates have that many votes, he wins all the district's delegates.
Sample 2012 Republican Primary Illinois Ballot
Therefore, vote-splitting is a real factor. If the delegate vote splits 34%-33%-33% and Romney gets the 34%, then he wins the delegates, the other candidates get nothing.