Gorge yourself on media spin much? This is nothing more than a media created myth. This is what they want you to believe. What is the evidence for it though? Head to head polling nationally? At this point that polling is meaningless. But even so, most of the head to head polling shows that the only serious candidate that is havimg trouble beating Hillary is Trump.
If that is not enough, the competition is a highly unliked Nurse Ratched figure that is under FBI investigation for illegally handling and distributing classified information. Nurse Ratched may actually end up being indicted before we get to the general. The other decrepit contender is a 70+ old, hippie, socialist for the 60's. The Democrats are putting forth the weakest field I've ever seen. That's saying something when you consider Al Global Warming Gore and John I Served in Vietnam Kerry. I submit that I could probably shave my dogs butt, tattoo a R on it, make him walk backwards, and he could probably beat these two. The strength of these two is over-hyped.
Lastly, remember how the establishment told us that Reagan couldn't win. The measures they took to stop Reagan reached hysterical levels. Seems history repeats itself.
The establishment and it's media arms (led by Fox News) are going to sell Rubio hard as the "only one". This is pure propaganda.
You should base you choice on the merits of the candidates and not the media created hype. Of any election cycle where this would be true, it is most certainly this one.
My opinion about Cruz is not based on any particular source other than my own gut. Once the democrats unload on Cruz I don't think he would carry 5 states.