It's not likely he is switching parties unless he is not a true believer in limiting the role of Gov't. The fact that people critique his speech because he needed a drink of water rather than address the substance of his speech shows how pathetic politics has become. This type of pathetic focus is why the sheep are allowed to be led around by the nose by the media into believing that people who believe in limiting the role of gov't must somehow be a racist or bigoted. (Even though Republicans have far more often appointed women and minorities into cabinet level positions) Few people are actually listening to substance. The reality is the Rubio to date has demonstrated himself to be a fairly strong advocate for limiting gov't. Until he shows otherwise, which he may do, I could care less how many drinks of water he needs.
His biggest problem is he comes from the Senate. And generally speaking congressman have no experience making individual decisions that they have to be held accountable for unless they have held a prior role in the private sector or state govenership. That often leads to terrible leadership, as we see with our current President. Electing someone soley based on charisma with little experience is something to be cautious about. Unfortunately, many Americans don't vote on policy as recent elections have demonstrated. On specific policy positions Obama was losing in nearly every area. Yet, he sounds good and people like him personally so they vote for him. Many Republicans think Rubio has the same charisma and consider him a leader based on that alone. I think he is a natural leader as well, but I am more interested in his policy positions. Not the hollywood like obsession with someone's haircut, walk, the shape of their chin, or how much water they drink in a speech. Because should he run for higher office, he won't have the mainstream media in his back pocket like Obama does. In all probability Rubio would not win a primary anyway and more likely be a VP candidate at best in 4 years.
The attraction to Rubio, is that a large number of hispanics hold very conservative values and agree with the GOP on many issues. But oppose the way the media has been able characterize the position of conservatives on the issue of immigration. They home that Rubio can better articulate the position without the media being able to distort the message by speaking directly to hispanics. That will make him a lightening rod for the mainstream.