I'm not baffled. Given the number of GOP voters for whom Trump is their last choice, he was probably going to have a max somewhere in the mid-twenties.
And given the anti-Cruz flak from all corners in the last two weeks, he was not well positioned to build a lead.
Someone had to capitalize, and it turns out to be Rubio.
Remember that the GOP electorate is not Free Republic writ large. I imagine that a third of the caucus goers could contentedly vote for establishment candidates.
“Remember that the GOP electorate is not Free Republic writ large.”
That really stood out for me for the first time in the 2008 primaries when the main FR candidates were Tancredo, Hunter and Fred Thompson.