Be careful not to assign too much scientific precision to polls. They aren't as accurate as portrayed. But several different surveys at roughly the same time that show similar results are useful guides. So three trends in recent polls must worry Sen. Barack Obama and encourage Sen. John McCain.
First, an average of seven national polls the week before the Democratic convention showed Mr. Obama leading Mr. McCain by two points. By the middle of the next week, Mr. Obama's lead had climbed to almost eight points. Now, nearly two weeks later, Mr. McCain has a lead of roughly two points. Since the middle of the GOP convention, one out of every 10 voters has changed their preference -- a significant movement this late in the campaign.
FULL ARTICLE: http://online.wsj.com/article/SB122169427700049941.html
