A recent USA TODAY/CNN/Gallup Poll finds that Pres. Bush leads Sen. Kerry 50%-46% among likely voters.
"The survey showed Kerry losing 1 percentage point and Bush gaining 4 percentage points from a poll taken the week before the Boston convention."
"The change in support was within the poll's margin of error of +/-4 percentage points in the sample of 763 likely voters. But it was nonetheless surprising, the first time since the chaotic Democratic convention in 1972 that a candidate hasn't gained ground during his convention."
It's quite easy to see why Bush might have gotten a bounce from the DNC. There was a week of News focusing on the convention and NOT the bad news or perceived bad news from Iraq. This election is not about why Kerry should be elected but rather about why Bush Should not be reelected.
Generally a reelection campaign for president is more about the incumbent rather than the challenger. In this type of election the electorate usually answers two questions, 1. "does the incumbent deserve a second term?", and if the answer to that is NO, than 2." is the challenger an adequate replacement?" My point is, the electorate needs to decide if they want get rid of the incumbent before they decide on the challenger. The Burden is on the challenger to show the electorate that the incumbent needs to be replaced. The incumbent needs to defend their record and show that, even if the electorate wants the president gone, the challenger is not an adequate replacement. Look at the 96 election, because the economy was good, we were in a "perceived time of peace", and despite all of Clinton's scandals and questionable behavior, the electorate was happy and did not see a reason to replace him, therefore he won by a fairly comfortable margin. A Reagan type Republican running against Clinton in 96 would have lost because the electorate decided that Clinton deserved a second term.
When the news does not favor removing President Bush, like bad news from Iraq or the economy, Kerry will drop in the polls! That is why, considering the coverage for the past week focused on the convention, Bush could have received a Bounce in the polls from the DNC.