Yes. Candidates can get eliminated for the Dumbest reasons.
Just as Dukakis and Dean.
Unfortunately for him, It shows him forgetting a fundamental pillar of his economic plan while repeatedly stating
...um... a eliminate education...um a...eliminate education...um a... eliminate education....
he has opened up himself to the very obvious criticism, "If he took education more seriously, perhaps he wouldn't have made such a blunder."
Yes, he is no longer a serious contender, but not simply because of this flub. This is only one of a long line of flubs he has made. It's the final nail in the coffin, that's all.
ETA: As Tricky pointed out, his flub (and all the others) alludes to a shallow campaign.