You hate to point out things that should not need explanation, but for the record:
1) The grass is always greener. Many Republicans are crossing their fingers and saying their prayers that Chris Christie will "save them" by deigning to enter the race. Many Republicans, including some of the same people, were praying two months ago that Rick Perry would save them. Before that, some of them wished that Jon Huntsman would save them. Whatever Christie does, some will starting yearning for Paul Ryan to save them. Or Jeb Bush. Or Mitch Daniels. Or whatever other name I am forgetting just now.
Here's the truth. In modern politics, "savior" candidates are never again as popular as they are the day before they announce. To start down the list of reasons: Neither opposing candidates nor the press can unleash all-out hostile-investigative scrutiny on a mere "potential" candidate. But the instant the candidate declares, anything goes. A teasing, courted candidate in "will he or won't he?" mode -- Chris Christie, as of this moment -- spends all day every day being told how great he is. A real candidate spends all day begging for money; facing the risk of errors; and knowing the certainty of making enemies and giving offense. The errors come from debates, press ops, responses to criticism. The offense comes from having to choose sides on policy issues that a non-candidate can ignore or finesse.