Well that is an 'undeclared' point since there's nothing 'official' stating there were only going to be two candidates in this first debate...
...further... making it appear that this one debate will decide the fate of the primary election is foolish at best.
Romney has already been fully vetted and already has all the money he needs and is too cautious to implode. So if you succeed in mortally wounding Perry, you will just be handing the nomination to Romney, and nothing you can say or do with keep Romney from getting the nomination then.
Once you realize that Romney was going to get the nomination easy, you will see Perry as I do, as the man who saved us from Romney. Prior to Perry's entry into the race all the other candidates also knew Romney was going to win judging how debate after debate they never went after him and in fact went out of their way not to attack him. They are all running for vice president and they know it.