The Monday night debate in Florida was the beginning of the end. He won SC by attacking liberals. He had two great days in Florida by attacking liberals (Sunday and Monday during the day). He came into that Monday debate with a big lead in Florida and nationwide. Just two days after big SC win.
Then - and maybe you and I disagree on this - then he let Mitt drag him off the subject of liberals and onto the subject of each other - and that was it.
He was outspent on negative ads 65 to 1 in Florida, and he was off message. His only chance was to stay focused on liberals because folks love Newt when he attacks liberals, not so much when he attacks other Republicans or when he defends himself.
But that fits in nicely with my timeline.
I have no disagreement with your analysis (up to a point), as I now recall. Newt suggested that the candidates refrain from attacking each other in response to the baiting questions - but - Mitt was there to take Newt out and would not be deterred from delivering his attack lines.
The point where I would go a bit further is: Newt should have realized that Romney is just another LIBERAL and dealt with him from that perspective.
He was certainly caught off guard and that indicates a weakness/flaw. I would like to see him get the opportunity to show that he has corrected this weakness/flaw.