Barack Obama has so far received anywhere from a 5 to 8 point bounce from the Democratic National Convention (depending on when it's measured from), and now leads John McCain 48 to 42 in the latest Gallup tracking poll.
There is a lag of sorts involved in the daily tracking; interviewing is conducted in most parts of the country before that evening's high-focus speeches have taken place. Thus, the current three-day average would reflect any impact of Monday night's speech by Michelle Obama, and Tuesday night's speech by Hillary Clinton, but would not completely reflect Wednesday night's lineup of speakers, such as John Kerry, former President Bill Clinton, and vice presidential nominee Joe Biden, nor the appearance on stage at the end of the evening by Barack Obama himself.
Since I thought last night was the strongest, I would say that this is a solid but not overwhelming bounce for Obama. With McCain's VP choice set to be formally announced tomorrow (though possibly leaked this evening) and the Republican National Convention starting up on Monday, any bounce is likely to be short-lived. Remember that Obama went up by 9 points initially when on his European trip, but that quickly evaporated as McCain unvieled a series of sharp attacks, including the celebrity ad. Really, we won't see any meaningful polling until the week of Sept. 8, after Americans have digested both conventions. But it's hard to look away.