Why is everybody burying Rubio after a single debate performance?

[Mehmentum]

1.) This happened at the worst possible time. New Hampshire was supposed to be Rubio's breakout moment.  If it doesn't happen here, he's not going to get it until after Super Tuesday.  

And it happened right before the New Hampshire primary.  This horrible, disastrous debate performance will be the narrative on election day.  This is what all of the undecided voters and weak Rubio supporters are going to hear about Rubio.  There's no time for another news cycle, there's no time for redemption or damage control.

2.) Rubio's support is soft. The good news cycle after getting in third in Iowa lifter Rubio's polling in NH from 9-10% to about 16%.  Those new converts aren't going to stick around when the cycle turns against him.  10% of the vote isn't going to get Rubio 2nd place, or even 3rd place most likely.  

This assumes none of Rubio's more solid supporters don't get second thoughts for one of the establishment candidates (or even Cruz).  Rubio isn't like Trump, he doesn't have that many die hard fans.

3.) Rubio has opponents nipping at his heels.  There are three candidates who are just itching to snatch up his voters and potential voters.  Even worse, if even one of these people finishes ahead of him, Rubio's path to the nomination becomes that much harder.  Not only will he have to deal with the electoral calendar being stacked against him for the next month, he's going to be in the fight of his political life against another establishment candidate.  This is all while Cruz and/or Trump rack up win after win.

This is ignoring the fact that Rubio's debate performance wasn't just poor, but without a doubt the greatest meltdown of this cycle.  I don't feel like arguing about that particular point anymore.  Suffice it to say that this doesn't need to be an 'Oops' level blunder to ruin Rubio's chances.