This is what it is. A rumor. But it is a rumor sufficiently well-placed that Bill Kristol feels comfortable running with it:
Trump 32; Cruz 26; Rubio 20; Bush 10; Carson 7; Kasich 2.
Keep in mind this is not an internal campaign poll but one that will be published in the next day or so.
Compare and contrast with the trend lines.
If true, what it shows is that supporters of other candidates have moved to Cruz and Rubio. Kasich is what he's always been: a vanity candidate. More importantly, Trump has lost six points since November.