It may have taken a little while for the CNN Democratic debate to get going — it took more than eight minutes for the first question to be asked, thanks to lengthy introductions and pre-debate predictions — but once it started, things got feisty very quickly. One reason for that may be the lenient rules of the debate moderated by Wolf Blitzer, who has allowed candidates to interrupt each other and follow up to each other's answers, in addition to cheers and clapping from the crowd throughout every answer.

Sen. Hillary Clinton and Sen. Barack Obama had a lengthy back-and-forth about the issue of Obama's Reagan reference. Clinton attacked Obama over the comment, and upon pushing back, Obama brought up "Boom."

"The irony of this is that you provided much more fulsome praise of Ronald Reagan in a book by Tom Brokaw that's being published right now," Obama said.

The exchange left John Edwards exasperated, asking if there were "three people in this debate." After a subsequent answer was stopped by Blitzer, Edwards said, "Let me finish, lord knows you let them go on forever."

The crowd let loose with more huge applause and cheers.

Update: Click continued to see the full Clinton-Obama exchange from the debate...