I would agree that it will likely come down to Rubio and Trump. I know before Saturday, some people had Kasich possibly emerging as the voice of GOP reason, but his dismal showing this weekend is slotting him firmly in VP-at-best territory.
I'm noting a tone shift in the coverage on Trump. It seems like all articles are devoting a full paragraph or more on the fact that if any other GOP candidate was doing as well as Trump, that candidate would be called the 'prohibitive favorite' but because it's Trump, it feels weird to say that.