Consider three data points about Jeb Bush.
First, his campaign and Super PAC combined threw everything they possibly could at Marco Rubio — from attack to inuendo — and failed to take out Rubio. Chris Christie, in two minutes on a debate stage, did what Team Jeb could not. Christie may have committed a murder suicide with Rubio, but his two minute stunt on the debate stage was far more effective than the millions spent by Team Jeb.
Second, consider the Bush campaign tone deafness accusing Marco Rubio of wanting a coronation when Bush tried to raise massive amounts of money, secure every possible consultant and donor, and walk into the nomination — a process that sparked the rise of Trump.
Third, Jeb Bush spent approximately $1200 per vote to come in fourth in New Hampshire. Jeb Bush has no viable path forward with that burn rate to come in fourth. His performances have been staggeringly awful.
To go out on stage in New Hampshire and tell the crowd that his campaign is not dead is an admission against interest that the campaign is dead.