"CNN analysts will make all projections for CNN broadcasts. When CNN's analysts project a winner in a race, whether it is based upon data from EMR or from the CNN computations, it means that when all the votes are counted, CNN projects that the candidate will win the race. A projection is as close to statistical certainty as possible, but that does not mean that a mistake cannot happen; rather, it means that every precaution has been taken to see that a mistake is not made. CNN will not "declare" someone a winner because that declaration is up to election officials. CNN will make projections based on our best estimate of how CNN expects an election to turn out."

From CNN, anyway.