The Gallup Daily Presidential tracking poll, which many of us follow more closely than we should, reports results based on a survey of registered voters. At some point in the future, Gallup is going to switch to likely voters for the tracking poll, but we don't know exactly when.
Just as Nate predicted over at 538, the Gallup tracking poll showed a stable, close race leading up to the conventions, then a bounce for Obama, and then a bounce for McCain that seems to be subsiding, though less quickly than Obama's. The longer-lasting effect of McCain's bounce is probably the result of his VP selection (and convention) stepping on Obama's, rather than any lasting shift in the race (despite what the pundits have rushed to conclude).
That poll, taken in the three days immediately following the Republican National Convention, showed by far the largest national lead McCain has ever had in any poll (54-44 among likely voters), and generated a tremendous amount of attention. It helped drive the buzz for all of last week -- that McCain got a huge bounce from his convention, that Palin was a game-changer, that Obama was in big trouble, etc.
Notice that Gallup never released a likely voter poll over the three days immediately following the Democratic convention -- nor did it release any polls through USA Today during Obama's bounce. Putting it in USA Today guarantees far greater attention than the tracking poll alone gets.
http://www.dailykos.com/story/2008/9/15/74531/5933/788/599244