Look at the latest polls tracked by RCP:link
Up until about a week and a half ago, there was only one poll ever that had Obama as high as 24%. Now the last four polls in a row (ABC/Wash Post, Rasmussen, Time, Zogby) all have Obama at 24% or higher.
On the GOP side, up until recently, there had only been one poll ever that had Giuliani's lead over McCain as high as 16 points. Now four of the last five polls have Giuliani ahead by at least 16 points.