One reason Ted Cruz has been so adept is that he’s been running a campaign in a conservative primary pretty much continuously since he announced for the Texas senate in January 2011. If you do this for years, and it’s all you’ve been doing, you will get good at it, especially if you have the native talent of Cruz.
The contrast couldn’t be any starker with Jeb Bush, who last ran in an election in 2002 and last ran in a meaningful primary in 1994. Cruz and Bush are obviously very different people with very different theories of what the GOP should be, but one of them is completely on his game and the other has been getting up to speed while running a presidential campaign.