The crazy Texas Tea Party, plus the general wing nuttery of the Texas republicans in general will elect Cruz in the primary. Dewhurst is viewed pretty much like Kay Bailey was. The wingers in the right are just digging in further into crazy.
And unfortunately, as was mentioned above by NoPasaran, we are not poised for a pick up, no matter how crazy Cruz is. Texas voters are still very loyal to the Rs in this state in general elections. And without major national resources, even by 3rd party groups like the Club for Growth throwing a million dollars behind Cruz, we will be outspent 10 to 1 or even 20 to 1.