I suspect it's too late, but it's good. Mittens needs to be challenged as much as possible, to get in maximum shape to take on Obama. Exercise is good, and more exercise is better! Perry obviously is just a punching bag for Mittens, and no challenge at all. It's like lifting just the bar on the bench press, without any weights on it - sort of like I do just to get warmed up a bit, before adding the iron. Christie will be more formidable. And Christie if he wins hopefully will not be in the DOA category for the finals that Perry would be in my judgement.
Torie, I respectfully disagree. Christie is a not merely a warm-up test... He has the ability (unlike any of the others, save Huntsman) to directly compete for Romney's voters. He's a Northeasterner who certainly could compete in states like New Hampshire. I know plenty of people (including my mother) who are planning to vote for Romney but would switch to Christie in a heartbeat should he announce.
Now, I doubt Christie will run, but his colorful, all-encompasing appeal would vault him to the first tier instantly.