NPR is projecting that Barack Obama has won the Georgia primary. You can continue to follow results state by state here and on our NPR Election Map.

So how are projections like this made, before the votes have been tallied? They use exit polls. Voters are surveyed as they leave their polling place about who they voted for. It's only a sample, not every voter, so that information is combined with pre-election polling, how voters in that precinct have previously voted, and other information to project a winner. They often wait until actual results start getting reported, figuring those into the calculations, to make sure an accurate projection is made.