You are wrong on that score. One of Zogby's favorite tactics is to have "dramatic last minute surges" in the closing days of the campaign. Thus, he could have the race close the entire way, but then claim that Bush gained 10 points in the final two days of his tracking poll and claim he was right all along. He does this quite often, but people keep falling for it.
There are a lot of people in the polling business. If Zogby did that, wouldn't others say something? Zogby can't be keeping his methods secret; if he were we would be talking about that.
Excuse me but there is a difference between a poll 40 days out and one the weekend before the election. A poll taken now is basically for entertainment value, a way to get a feel for the horserace. The final polls taken prior to the election are predictions. In the final polls, Zogby and others make assumptions about turnout by party and other factors to make their final prediction as valid as they can. In 2000 the race collapsed in the last few days because Bush didnt come clean with the DUI information early on in the campaign by mentioning that he had been arrested for DUI when he was young and irresponsible. When the charges came out the final weekend there was no time for Bush to deflect the charges or voters to process them.
I've long suspected that too. And not just about Zogby's polls.
Btw, as a sidenote: I heard that Gallup explains its difference from other polls by its methodology. Gallup simply asks pollees, straight out, whom they're voting for.
Whereas Zogby et al ask a long list of leading questions first, before springing the 'Bush or Kerry' question at the very end.