Next Monday will be the 3rd of October. Aren't we really stretching the boundaries of how late a candidate can enter at that point? It'd be a mere 3 months until caucus time.
I think people are really underestimating the insanity of getting in this late as it relates to organizing in the early states... people don't just show up to these caucuses and primaries on their own; the campaign has to work to get them there and Christie has no infrastructure whatsoever to support that. I think his performance in Iowa and New Hampshire would end up being significantly less than whatever he would end up polling there the day before the elections.