This has been a mainstream media talking point for the past couple of days now, and its quite tiring. Everybody treats Marco Rubio as if he's the real deal, even though he does worse than Paul and Cruz in all the polls. Rubio is more of the same for conservative politics, whereas Paul and Cruz are drastically different and would make changes. People don't seem to like change, so they brush them off as joke candidates.
I feel like it may become a self fulfilling prophecy though. Like, a lot of random Republican primary voters thinking: "Hmm, what about Rubio? That guy that every media outlet in the country spams is a top tier contender and a great candidate? Sure, I guess I'll support him."