Also notice that in the head-to-head numbers, Bush is where he was, vis-a-vis Kerry, back at the end of January. Six months of Kerry's string of primary victories, and then strutting around as the Dem candidate in waiting, have been neutralized.
I'll tell you in two words why Bush has pulled ahead and it really isn't a big secret: Bill Clinton. He makes the President look good next to any other Democrat who is running. And the Clinton nostalgia among the Left unleashed with the release of Bubba's new book is causing many Lefties to pine for Hillary. I wouldn't be surprised in the least if the Democrats want to wait til 2008.