Think about it. Cruz as VP, a very smart and experienced lawyer who knows and loves the constitution. A little in the background, undoing the damage Obama and the Supreme Court have done to the Constitution. Four (or eight) years of Trump, then eight years of Cruz. It doesn't work the other way, because Trump's age would become an issue in eight years. With that many years (12 or 16), maybe the US can be saved. And Cruz could bring along some younger politicians to keep it going.
Cruz is needed to replace Ginsburg or Breyer.