A lot of people will be deceiving themselves before this day is done, but don't let anyone deceive you: there are only three tickets (at most) out of New Hampshire, and Donald Trump and Ted Cruz already own two of them. Since 1968, no candidate has ever won the nomination without winning either Iowa or New Hampshire.
The unique political phenomenon that is Donald Trump might allow that to happen this year, especially given Rubio's surprise finish in Iowa. However, that person would have to either be Marco Rubio, or would have to beat him convincingly enough tonight to erase the Iowa momentum. And however Joe Scarborough and the rest of the fanboys of the establishment lane candidates might try to spin it, one bad moment in one debate won't undo the momentum Rubio built from the counting of actual votes last Monday - it will take a convincing defeat at the polls for that to happen.
Ben Carson is already done for. After finishing fourth in Iowa, and with no reasonable shot of a top 3 finish in New Hampshire, Carson is just looking for excuses to continue milking donors at this point. He's also playing the useful fool for Trump against Cruz, but that is another issue altogether. Fiorina is likewise DOA and her VP audition will begin in earnest on Wednesday.
This leaves Jeb, Kasich, and Christie on the outside looking in, fighting with Rubio for the last remaining feasible spot in the race coming out of New Hampshire.
In order to have a reasonable chance of taking Rubio's spot, it should go without saying that the very least they must accomplish is to defeat Rubio. If Rubio finishes second, or third behind Trump and Cruz, it's time for Jeb, Kasich and Christie to go home; they threw everything they had at a very moderate electorate in New Hampshire, and failed to even get the bronze. Realistically, one of this three (most likely Kasich) probably also needs to defeat Ted Cruz and finish second.
Otherwise, both Rubio and Kasich/Jeb/Christie will emerge from New Hampshire with delusions of viability, the end result being the more or less permanent split of the not-Trump/Cruz vote, and the eventual nomination of Trump.
Either way, at the end of the night, there will be one Establishment candidate left standing - or if there is more than one left standing, there will really be no Establishment candidates left standing and we can all get ready to order our Republicans for Hillary T-Shirts.
Welcome to New Hampshire. Four candidates enter, one will leave.