John, it’s not just the Gallup tracking poll that is so dramatic; the RealClearPolitics.com poll average now shows John McCain up by over three points. It is worth considering how Barack Obama missed, as you point out, a golden opportunity in Denver to reach out to swing voters and seize a commanding lead. Why the angry, liberal screed?

This is the best I can come up with:

 1) The Obama camp is convinced they can pull a “Karl  Rove” and win on turnout of their base — college kids, elites,etc. (this was before Sarah Palin juiced the GOP base). The speech was red meat for them — an effort to bolster their turnout and excitement that flagged under the “Celebrity” ad and flip-flop criticisms during the summer.

2) The Democrats are obsessed with Swift Boating and think they lose because they don’t hit back hard enough and beat those mean Republicans at their own game. So Demver was the pre-emptive, paranoid attack on McCain. In the process Obama lost the independent voters.

McCain made no such error and of course found the one person who could excite his base and reach disaffected Hillary voters. On such decisions elections turn.