I think Christie would be a magnificent candidate, and wish he would get in the race. There is still time.....
I really like Christie and I like Walker but I agree with Christies decision not to run for POTUS right now. New governors like them need to serve their (first) terms to completion and then get re-elected after the budget cuts and tax cuts are shown to be a success, and then they will be powerful forces as well as examples of success that we need. It is not their time yet and it does not make me happy to accept this.
Christie as governor of a liberal state will attract a deal criticism for some of his positions, ones that I wont mention now since he is not running for POTUS. Something to keep in mind.