He did, he called Rubio out on his promoting Reid's amnesty bill and Rubio said that it was a lie, and when Trump was asked about it he agreed with Rubio, that Cruz was lying.
Clearly Trump's strategy is to smear and destroy Cruz first, even when it means defending Rubio like this, then go after Rubio last.
When the time comes Trump will flip for the ...0000..... time and attack Rubio on his amnesty bill. The way things are going it will probably work for him again, in this primary.
His “The Joker high on acid” style attacks on Cruz have been just appalling. If his hope is to have the support of Cruz backers one on one with Rubs......speaking for myself, not mine, Donnie.