He behaves the same when questioned about Obama.
Not true. He may reach the same conclusion, but the atmosphere is different.
And you miss another key point, the situation is totally different with Obama. He is already President, so the question becomes how to BEST save the Republic from Obama. The answer is NOT the birther issue, for many many reasons, since that will never remove him from office and in fact, will probably strengthen him. Cruz is not President, so it's just an entirely different dynamic, keying on the intent of the Founders. And the intent was NOT NOT NOT to keep someone like Cruz from running.