By continuing to stand on principle and clearly articulating his message.
Alien concept these days, eh?
Three videos that I have seen from Cruz that show me principles can win:
1. Speaking to Middle Eastern Christians, Cruz suggests persecution is bad, even for Jews. The crowd boos - Cruz leaves. "If you will not stand with Israel [you filthy bigots], then I will not stand with you." He looked great as a result. (I may have added some subtext there.)
2. An illegal immigrant at one of his rallies tells him how "scared" she is that he will deport him. He says, "Yep, our broken system creates human tragedies, but we're a country of laws, so I will deport you." Excellent!
3. An Iowa farmer tells Cruz he can't support him because Cruz doesn't support the subsidies. Cruz very carefully articulates why the subsidies are bad, and how he can actually do better without them.
In all cases, the man didn't pander. He stood on principle and sounded mature and great - like a leader.